diff --git a/packages/client/src/account.ts b/packages/client/src/account.ts
index 5859bdead..2957ab085 100644
--- a/packages/client/src/account.ts
+++ b/packages/client/src/account.ts
@@ -55,7 +55,7 @@ export async function signout() {
 export async function getAccounts(): Promise<
 	{ id: Account["id"]; token: Account["token"] }[]
 > {
-	return (await get("accounts")) || [];
+	return (await get("accounts")) ?? [];
 }
 
 export async function addAccount(id: Account["id"], token: Account["token"]) {
diff --git a/packages/client/src/components/MkAbuseReportWindow.vue b/packages/client/src/components/MkAbuseReportWindow.vue
index c6fc768a6..e93b834f8 100644
--- a/packages/client/src/components/MkAbuseReportWindow.vue
+++ b/packages/client/src/components/MkAbuseReportWindow.vue
@@ -59,7 +59,7 @@ const emit = defineEmits<{
 }>();
 
 const uiWindow = ref<InstanceType<typeof XWindow>>();
-const comment = ref(props.initialComment || "");
+const comment = ref(props.initialComment ?? "");
 
 function send() {
 	os.apiWithDialog(
diff --git a/packages/client/src/components/MkAutocomplete.vue b/packages/client/src/components/MkAutocomplete.vue
index 5fcee6e5a..3a97f4584 100644
--- a/packages/client/src/components/MkAutocomplete.vue
+++ b/packages/client/src/components/MkAutocomplete.vue
@@ -268,7 +268,7 @@ function exec() {
 	} else if (props.type === "hashtag") {
 		if (!props.q || props.q === "") {
 			hashtags.value = JSON.parse(
-				localStorage.getItem("hashtags") || "[]",
+				localStorage.getItem("hashtags") ?? "[]",
 			);
 			fetching.value = false;
 		} else {
diff --git a/packages/client/src/components/MkCaptcha.vue b/packages/client/src/components/MkCaptcha.vue
index 146c512fb..76c9b91fe 100644
--- a/packages/client/src/components/MkCaptcha.vue
+++ b/packages/client/src/components/MkCaptcha.vue
@@ -78,14 +78,14 @@ const src = computed(() => {
 });
 
 const captcha = computed<Captcha>(
-	() => window[variable.value] || ({} as unknown as Captcha),
+	() => window[variable.value] ?? ({} as Captcha),
 );
 
 if (loaded) {
 	available.value = true;
 } else {
 	(
-		document.getElementById(props.provider) ||
+		document.getElementById(props.provider) ??
 		document.head.appendChild(
 			Object.assign(document.createElement("script"), {
 				async: true,
diff --git a/packages/client/src/components/MkDateSeparatedList.vue b/packages/client/src/components/MkDateSeparatedList.vue
index 6699f0313..8dae76ba8 100644
--- a/packages/client/src/components/MkDateSeparatedList.vue
+++ b/packages/client/src/components/MkDateSeparatedList.vue
@@ -50,7 +50,7 @@ export default defineComponent({
 
 		const renderChildren = () =>
 			props.items.map((item, i) => {
-				if (!slots || !slots.default) return;
+				if (slots == null || slots.default == null) return;
 
 				const el = slots.default({
 					item,
diff --git a/packages/client/src/components/MkDialog.vue b/packages/client/src/components/MkDialog.vue
index a5e553a5e..40332e3d5 100644
--- a/packages/client/src/components/MkDialog.vue
+++ b/packages/client/src/components/MkDialog.vue
@@ -65,8 +65,10 @@
 				v-model="inputValue"
 				autofocus
 				:autocomplete="input.autocomplete"
-				:type="input.type == 'search' ? 'search' : input.type || 'text'"
-				:placeholder="input.placeholder || undefined"
+				:type="
+					input.type === 'search' ? 'search' : input.type ?? 'text'
+				"
+				:placeholder="input.placeholder ?? undefined"
 				:style="{
 					width: input.type === 'search' ? '300px' : null,
 				}"
@@ -294,7 +296,7 @@ const okButtonDisabled = computed<boolean>(() => {
 	if (props.input) {
 		if (props.input.minLength) {
 			if (
-				(inputValue.value || inputValue.value === "") &&
+				inputValue.value != null &&
 				(inputValue.value as string).length < props.input.minLength
 			) {
 				disabledReason.value = "charactersBelow";
diff --git a/packages/client/src/components/MkDrive.file.vue b/packages/client/src/components/MkDrive.file.vue
index 5105fc0f0..fce7646e7 100644
--- a/packages/client/src/components/MkDrive.file.vue
+++ b/packages/client/src/components/MkDrive.file.vue
@@ -185,7 +185,7 @@ function describe() {
 		},
 		{
 			done: (result) => {
-				if (!result || result.canceled) return;
+				if (result == null || result.canceled) return;
 				const comment = result.result;
 				os.api("drive/files/update", {
 					fileId: props.file.id,
diff --git a/packages/client/src/components/MkDrive.vue b/packages/client/src/components/MkDrive.vue
index 1ca9b2ff0..e22594d9a 100644
--- a/packages/client/src/components/MkDrive.vue
+++ b/packages/client/src/components/MkDrive.vue
@@ -363,7 +363,7 @@ function urlUpload() {
 		type: "url",
 		placeholder: i18n.ts.uploadFromUrlDescription,
 	}).then(({ canceled, result: url }) => {
-		if (canceled || !url) return;
+		if (canceled || url == null) return;
 		os.api("drive/files/upload-from-url", {
 			url,
 			folderId: folder.value ? folder.value.id : undefined,
diff --git a/packages/client/src/components/MkEmojiPicker.vue b/packages/client/src/components/MkEmojiPicker.vue
index bdd934492..4b0d8702f 100644
--- a/packages/client/src/components/MkEmojiPicker.vue
+++ b/packages/client/src/components/MkEmojiPicker.vue
@@ -106,7 +106,7 @@
 								.map((e) => ':' + e.name + ':')
 						"
 						@chosen="chosen"
-						>{{ category || i18n.ts.other }}</XSection
+						>{{ category ?? i18n.ts.other }}</XSection
 					>
 				</div>
 				<div v-once class="group">
@@ -423,7 +423,7 @@ function reset() {
 function getKey(
 	emoji: string | firefish.entities.CustomEmoji | UnicodeEmojiDef,
 ): string {
-	return typeof emoji === "string" ? emoji : emoji.emoji || `:${emoji.name}:`;
+	return typeof emoji === "string" ? emoji : emoji.emoji ?? `:${emoji.name}:`;
 }
 
 function chosen(emoji: any, ev?: MouseEvent) {
@@ -450,7 +450,7 @@ function chosen(emoji: any, ev?: MouseEvent) {
 }
 
 function paste(event: ClipboardEvent) {
-	const paste = (event.clipboardData || window.clipboardData).getData("text");
+	const paste = (event.clipboardData ?? window.clipboardData).getData("text");
 	if (done(paste)) {
 		event.preventDefault();
 	}
diff --git a/packages/client/src/components/MkFollowButton.vue b/packages/client/src/components/MkFollowButton.vue
index f52a685e6..c900d91b6 100644
--- a/packages/client/src/components/MkFollowButton.vue
+++ b/packages/client/src/components/MkFollowButton.vue
@@ -9,7 +9,7 @@
 	</button>
 	<button
 		v-if="!hideFollowButton && isSignedIn && $i.id != user.id"
-		v-tooltip="full ? null : `${state} ${user.name || user.username}`"
+		v-tooltip="full ? null : `${state} ${user.name ?? user.username}`"
 		class="kpoogebi _button follow-button"
 		:class="{
 			wait,
@@ -19,7 +19,7 @@
 			blocking: isBlocking,
 		}"
 		:disabled="wait"
-		:aria-label="`${state} ${user.name || user.username}`"
+		:aria-label="`${state} ${user.name ?? user.username}`"
 		@click.stop="onClick"
 	>
 		<template v-if="!wait">
@@ -141,7 +141,7 @@ async function onClick() {
 			const { canceled } = await os.confirm({
 				type: "warning",
 				text: i18n.t("unfollowConfirm", {
-					name: props.user.name || props.user.username,
+					name: props.user.name ?? props.user.username,
 				}),
 			});
 
diff --git a/packages/client/src/components/MkFormDialog.vue b/packages/client/src/components/MkFormDialog.vue
index 11f1d63e2..c7018e0c4 100644
--- a/packages/client/src/components/MkFormDialog.vue
+++ b/packages/client/src/components/MkFormDialog.vue
@@ -25,11 +25,11 @@
 						v-if="form[item].type === 'number'"
 						v-model="values[item]"
 						type="number"
-						:step="form[item].step || 1"
+						:step="form[item].step ?? 1"
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -48,7 +48,7 @@
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -65,7 +65,7 @@
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -79,7 +79,7 @@
 						v-model="values[item]"
 						class="_formBlock"
 					>
-						<span v-text="form[item].label || item"></span>
+						<span v-text="form[item].label ?? item"></span>
 						<template v-if="form[item].description" #caption>{{
 							form[item].description
 						}}</template>
@@ -90,7 +90,7 @@
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -109,7 +109,7 @@
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -132,7 +132,7 @@
 						class="_formBlock"
 					>
 						<template #label
-							><span v-text="form[item].label || item"></span
+							><span v-text="form[item].label ?? item"></span
 							><span v-if="form[item].required === false">
 								({{ i18n.ts.optional }})</span
 							></template
@@ -146,7 +146,7 @@
 						class="_formBlock"
 						@click="form[item].action($event, values)"
 					>
-						<span v-text="form[item].content || item"></span>
+						<span v-text="form[item].content ?? item"></span>
 					</MkButton>
 				</template>
 			</div>
diff --git a/packages/client/src/components/MkInstanceCardMini.vue b/packages/client/src/components/MkInstanceCardMini.vue
index bd7556f12..7654335b7 100644
--- a/packages/client/src/components/MkInstanceCardMini.vue
+++ b/packages/client/src/components/MkInstanceCardMini.vue
@@ -15,7 +15,7 @@
 			<span class="host">{{ instance.name ?? instance.host }}</span>
 			<span class="sub _monospace"
 				><b>{{ instance.host }}</b> /
-				{{ instance.softwareName || "?" }}
+				{{ instance.softwareName ?? "?" }}
 				{{ instance.softwareVersion }}</span
 			>
 		</div>
diff --git a/packages/client/src/components/MkInstanceTicker.vue b/packages/client/src/components/MkInstanceTicker.vue
index 65d7a85cb..1172da991 100644
--- a/packages/client/src/components/MkInstanceTicker.vue
+++ b/packages/client/src/components/MkInstanceTicker.vue
@@ -33,7 +33,7 @@ const ticker = ref<HTMLElement | null>(null);
 
 // if no instance data is given, this is for the local instance
 const instance = props.instance ?? {
-	faviconUrl: Instance.faviconUrl || Instance.iconUrl || "/favicon.ico",
+	faviconUrl: Instance.faviconUrl ?? Instance.iconUrl ?? "/favicon.ico",
 	name: instanceName,
 	themeColor: (
 		document.querySelector(
diff --git a/packages/client/src/components/MkMention.vue b/packages/client/src/components/MkMention.vue
index dd2c2e564..fccfa2f2a 100644
--- a/packages/client/src/components/MkMention.vue
+++ b/packages/client/src/components/MkMention.vue
@@ -11,7 +11,7 @@
 		<span class="main">
 			<span class="username">@{{ username }}</span>
 			<span
-				v-if="host != localHost || defaultStore.state.showFullAcct"
+				v-if="host !== localHost || defaultStore.state.showFullAcct"
 				class="host"
 				>@{{ toUnicode(host) }}</span
 			>
diff --git a/packages/client/src/components/MkMenu.vue b/packages/client/src/components/MkMenu.vue
index 35fb5a6bf..33eb677ba 100644
--- a/packages/client/src/components/MkMenu.vue
+++ b/packages/client/src/components/MkMenu.vue
@@ -21,7 +21,7 @@
 				<template v-for="item in items2">
 					<div v-if="item === null" class="divider"></div>
 					<span v-else-if="item.type === 'label'" class="label item">
-						<span :style="item.textStyle || ''">{{
+						<span :style="item.textStyle ?? ''">{{
 							item.text
 						}}</span>
 					</span>
@@ -50,7 +50,7 @@
 							class="avatar"
 							disable-link
 						/>
-						<span :style="item.textStyle || ''">{{
+						<span :style="item.textStyle ?? ''">{{
 							item.text
 						}}</span>
 						<span
@@ -76,7 +76,7 @@
 							v-if="item.icon"
 							:class="icon(`${item.icon} ph-fw`)"
 						></i>
-						<span :style="item.textStyle || ''">{{
+						<span :style="item.textStyle ?? ''">{{
 							item.text
 						}}</span>
 						<span
@@ -121,7 +121,7 @@
 							v-model="item.ref"
 							:disabled="item.disabled"
 							class="form-switch"
-							:style="item.textStyle || ''"
+							:style="item.textStyle ?? ''"
 							>{{ item.text }}</FormSwitch
 						>
 					</span>
@@ -136,7 +136,7 @@
 							v-if="item.icon"
 							:class="icon(`${item.icon} ph-fw`)"
 						></i>
-						<span :style="item.textStyle || ''">{{
+						<span :style="item.textStyle ?? ''">{{
 							item.text
 						}}</span>
 						<span class="caret"
@@ -166,7 +166,7 @@
 							class="avatar"
 							disable-link
 						/>
-						<span :style="item.textStyle || ''">{{
+						<span :style="item.textStyle ?? ''">{{
 							item.text
 						}}</span>
 						<span
diff --git a/packages/client/src/components/MkMiniChart.vue b/packages/client/src/components/MkMiniChart.vue
index bfa83f3d8..692e3b345 100644
--- a/packages/client/src/components/MkMiniChart.vue
+++ b/packages/client/src/components/MkMiniChart.vue
@@ -48,7 +48,7 @@ const color = accent.toRgbString();
 
 function draw(): void {
 	const stats = props.src.slice().reverse();
-	const peak = Math.max.apply(null, stats) || 1;
+	const peak = Math.max(1, ...stats);
 
 	const _polylinePoints = stats.map((n, i) => [
 		i * (viewBoxX / (stats.length - 1)),
diff --git a/packages/client/src/components/MkNote.vue b/packages/client/src/components/MkNote.vue
index 7c188047e..06d5d391c 100644
--- a/packages/client/src/components/MkNote.vue
+++ b/packages/client/src/components/MkNote.vue
@@ -375,7 +375,7 @@ const isForeignLanguage: boolean =
 	defaultStore.state.detectPostLanguage &&
 	appearNote.value.text != null &&
 	(() => {
-		const targetLang = (translateLang || lang || navigator.language)?.slice(
+		const targetLang = (translateLang ?? lang ?? navigator.language)?.slice(
 			0,
 			2,
 		);
@@ -395,7 +395,7 @@ async function translate() {
 	translating.value = true;
 	translation.value = await translate_(
 		appearNote.value.id,
-		translateLang || lang || navigator.language,
+		translateLang ?? lang ?? navigator.language,
 	);
 
 	// use UI language as the second translation language
@@ -403,7 +403,7 @@ async function translate() {
 		translateLang != null &&
 		lang != null &&
 		translateLang !== lang &&
-		(!translation.value ||
+		(translation.value == null ||
 			translation.value.sourceLang.toLowerCase() ===
 				translateLang.slice(0, 2))
 	)
diff --git a/packages/client/src/components/MkNoteSub.vue b/packages/client/src/components/MkNoteSub.vue
index 5bbb437b8..72ce89e76 100644
--- a/packages/client/src/components/MkNoteSub.vue
+++ b/packages/client/src/components/MkNoteSub.vue
@@ -292,7 +292,7 @@ const isForeignLanguage: boolean =
 	defaultStore.state.detectPostLanguage &&
 	appearNote.value.text != null &&
 	(() => {
-		const targetLang = (translateLang || lang || navigator.language)?.slice(
+		const targetLang = (translateLang ?? lang ?? navigator.language)?.slice(
 			0,
 			2,
 		);
@@ -312,7 +312,7 @@ async function translate() {
 	translating.value = true;
 	translation.value = await translate_(
 		appearNote.value.id,
-		translateLang || lang || navigator.language,
+		translateLang ?? lang ?? navigator.language,
 	);
 
 	// use UI language as the second translation language
@@ -320,7 +320,7 @@ async function translate() {
 		translateLang != null &&
 		lang != null &&
 		translateLang !== lang &&
-		(!translation.value ||
+		(translation.value == null ||
 			translation.value.sourceLang.toLowerCase() ===
 				translateLang.slice(0, 2))
 	)
diff --git a/packages/client/src/components/MkNotes.vue b/packages/client/src/components/MkNotes.vue
index 07ed2c3f1..3540677e2 100644
--- a/packages/client/src/components/MkNotes.vue
+++ b/packages/client/src/components/MkNotes.vue
@@ -28,7 +28,7 @@
 					class="notes"
 				>
 					<XNote
-						:key="note._featuredId_ || note._prId_ || note.id"
+						:key="note._featuredId_ ?? note._prId_ ?? note.id"
 						class="qtqtichx"
 						:note="note"
 					/>
diff --git a/packages/client/src/components/MkNotificationSettingWindow.vue b/packages/client/src/components/MkNotificationSettingWindow.vue
index df5d16246..d1bf7dd07 100644
--- a/packages/client/src/components/MkNotificationSettingWindow.vue
+++ b/packages/client/src/components/MkNotificationSettingWindow.vue
@@ -64,7 +64,7 @@ const props = withDefaults(
 	},
 );
 
-const includingTypes = computed(() => props.includingTypes || []);
+const includingTypes = computed(() => props.includingTypes ?? []);
 
 const dialog = ref<InstanceType<typeof XModalWindow>>();
 
diff --git a/packages/client/src/components/MkNotifications.vue b/packages/client/src/components/MkNotifications.vue
index 33e78881a..1cbf2e2c4 100644
--- a/packages/client/src/components/MkNotifications.vue
+++ b/packages/client/src/components/MkNotifications.vue
@@ -181,7 +181,7 @@ onMounted(() => {
 			}
 			for (
 				let i = 0;
-				i < (pagingComponent.value.items || []).length;
+				i < (pagingComponent.value.items ?? []).length;
 				i++
 			) {
 				if (
diff --git a/packages/client/src/components/MkNumber.vue b/packages/client/src/components/MkNumber.vue
index 2a86c5abb..9936a02ac 100644
--- a/packages/client/src/components/MkNumber.vue
+++ b/packages/client/src/components/MkNumber.vue
@@ -18,7 +18,7 @@ const tweened = reactive({
 watch(
 	() => props.value,
 	(n) => {
-		gsap.to(tweened, { duration: 0.6, number: Number(n) || 0 });
+		gsap.to(tweened, { duration: 0.6, number: Number(n) ?? 0 });
 	},
 	{
 		immediate: true,
diff --git a/packages/client/src/components/MkPagination.vue b/packages/client/src/components/MkPagination.vue
index a03a77dcd..7ae4d99e1 100644
--- a/packages/client/src/components/MkPagination.vue
+++ b/packages/client/src/components/MkPagination.vue
@@ -151,8 +151,8 @@ const init = async (): Promise<void> => {
 		.api(props.pagination.endpoint, {
 			...params,
 			limit: props.pagination.noPaging
-				? props.pagination.limit || 10
-				: (props.pagination.limit || 10) + 1,
+				? props.pagination.limit ?? 10
+				: (props.pagination.limit ?? 10) + 1,
 		})
 		.then(
 			(res) => {
diff --git a/packages/client/src/components/MkPostForm.vue b/packages/client/src/components/MkPostForm.vue
index 754814aa0..9f4db8b5d 100644
--- a/packages/client/src/components/MkPostForm.vue
+++ b/packages/client/src/components/MkPostForm.vue
@@ -389,7 +389,7 @@ const draghover = ref(false);
 const quoteId = ref(null);
 const hasNotSpecifiedMentions = ref(false);
 const recentHashtags = ref(
-	JSON.parse(localStorage.getItem("hashtags") || "[]"),
+	JSON.parse(localStorage.getItem("hashtags") ?? "[]"),
 );
 const imeText = ref("");
 
@@ -460,10 +460,10 @@ const canPost = computed((): boolean => {
 		!posting.value &&
 		(textLength.value >= 1 ||
 			files.value.length >= 1 ||
-			!!poll.value ||
-			!!props.renote) &&
+			poll.value != null ||
+			props.renote != null) &&
 		textLength.value <= maxTextLength.value &&
-		(!poll.value || poll.value.choices.length >= 2)
+		(poll.value == null || poll.value.choices.length >= 2)
 	);
 });
 
@@ -970,7 +970,7 @@ function onDrop(ev): void {
 }
 
 function saveDraft() {
-	const draftData = JSON.parse(localStorage.getItem("drafts") || "{}");
+	const draftData = JSON.parse(localStorage.getItem("drafts") ?? "{}");
 
 	draftData[draftKey.value] = {
 		updatedAt: new Date(),
@@ -990,7 +990,7 @@ function saveDraft() {
 }
 
 function deleteDraft() {
-	const draftData = JSON.parse(localStorage.getItem("drafts") || "{}");
+	const draftData = JSON.parse(localStorage.getItem("drafts") ?? "{}");
 
 	delete draftData[draftKey.value];
 
@@ -1013,7 +1013,7 @@ async function post() {
 				: undefined,
 		channelId: props.channel ? props.channel.id : undefined,
 		poll: poll.value,
-		cw: useCw.value ? cw.value || "" : undefined,
+		cw: useCw.value ? cw.value ?? "" : undefined,
 		lang: language.value ? language.value : undefined,
 		localOnly: localOnly.value,
 		visibility:
@@ -1065,7 +1065,7 @@ async function post() {
 						.filter((x) => x.type === "hashtag")
 						.map((x) => x.props.hashtag);
 					const history = JSON.parse(
-						localStorage.getItem("hashtags") || "[]",
+						localStorage.getItem("hashtags") ?? "[]",
 					) as string[];
 					localStorage.setItem(
 						"hashtags",
@@ -1184,7 +1184,7 @@ onMounted(() => {
 		autosize(textareaEl.value);
 		// 書きかけの投稿を復元
 		if (!props.instant && !props.mention && !props.specified) {
-			const draft = JSON.parse(localStorage.getItem("drafts") || "{}")[
+			const draft = JSON.parse(localStorage.getItem("drafts") ?? "{}")[
 				draftKey.value
 			];
 			if (draft) {
@@ -1194,7 +1194,7 @@ onMounted(() => {
 				visibility.value = draft.data.visibility;
 				localOnly.value = draft.data.localOnly;
 				language.value = draft.data.lang;
-				files.value = (draft.data.files || []).filter(
+				files.value = (draft.data.files ?? []).filter(
 					(draftFile) => draftFile,
 				);
 				if (draft.data.poll) {
diff --git a/packages/client/src/components/MkPostFormAttaches.vue b/packages/client/src/components/MkPostFormAttaches.vue
index ea051c58c..c364f5136 100644
--- a/packages/client/src/components/MkPostFormAttaches.vue
+++ b/packages/client/src/components/MkPostFormAttaches.vue
@@ -105,7 +105,7 @@ async function describe(file) {
 		},
 		{
 			done: (result) => {
-				if (!result || result.canceled) return;
+				if (result == null || result.canceled) return;
 				const comment =
 					result.result.length === 0 ? null : result.result;
 				os.api("drive/files/update", {
diff --git a/packages/client/src/components/MkReactionIcon.vue b/packages/client/src/components/MkReactionIcon.vue
index e9d5a198c..8dbebb0ec 100644
--- a/packages/client/src/components/MkReactionIcon.vue
+++ b/packages/client/src/components/MkReactionIcon.vue
@@ -1,7 +1,7 @@
 <template>
 	<MkEmoji
 		:emoji="reaction"
-		:custom-emojis="customEmojis || []"
+		:custom-emojis="customEmojis ?? []"
 		:is-reaction="true"
 		:normal="true"
 		:no-style="noStyle"
diff --git a/packages/client/src/components/MkSignin.vue b/packages/client/src/components/MkSignin.vue
index 10bcfc3bd..f849b5046 100644
--- a/packages/client/src/components/MkSignin.vue
+++ b/packages/client/src/components/MkSignin.vue
@@ -33,7 +33,7 @@
 					<template #suffix>@{{ host }}</template>
 				</MkInput>
 				<MkInput
-					v-if="!user || (user && !user.usePasswordLessLogin)"
+					v-if="user == null || (user && !user.usePasswordLessLogin)"
 					v-model="password"
 					class="_formBlock"
 					:placeholder="i18n.ts.password"
diff --git a/packages/client/src/components/MkSignup.vue b/packages/client/src/components/MkSignup.vue
index 189af53f5..216da220e 100644
--- a/packages/client/src/components/MkSignup.vue
+++ b/packages/client/src/components/MkSignup.vue
@@ -310,12 +310,12 @@ const host = toUnicode(config.host);
 const hcaptcha = ref();
 const recaptcha = ref();
 
-const username: string = ref("");
-const password: string = ref("");
-const retypedPassword: string = ref("");
-const invitationCode: string = ref("");
+const username = ref("");
+const password = ref("");
+const retypedPassword = ref("");
+const invitationCode = ref("");
 const email = ref("");
-const usernameState:
+const usernameState = ref<
 	| null
 	| "wait"
 	| "ok"
@@ -323,9 +323,10 @@ const usernameState:
 	| "error"
 	| "invalid-format"
 	| "min-range"
-	| "max-range" = ref(null);
-const invitationState: null | "entered" = ref(null);
-const emailState:
+	| "max-range"
+>(null);
+const invitationState = ref<null | "entered">(null);
+const emailState = ref<
 	| null
 	| "wait"
 	| "ok"
@@ -335,11 +336,12 @@ const emailState:
 	| "unavailable:mx"
 	| "unavailable:smtp"
 	| "unavailable"
-	| "error" = ref(null);
-const passwordStrength: "" | "low" | "medium" | "high" = ref("");
-const passwordRetypeState: null | "match" | "not-match" = ref(null);
-const submitting: boolean = ref(false);
-const ToSAgreement: boolean = ref(false);
+	| "error"
+>(null);
+const passwordStrength = ref<"" | "low" | "medium" | "high">("");
+const passwordRetypeState = ref<null | "match" | "not-match">(null);
+const submitting = ref(false);
+const ToSAgreement = ref(false);
 const hCaptchaResponse = ref(null);
 const reCaptchaResponse = ref(null);
 
diff --git a/packages/client/src/components/MkTokenGenerateWindow.vue b/packages/client/src/components/MkTokenGenerateWindow.vue
index 7e440c959..933e1ca91 100644
--- a/packages/client/src/components/MkTokenGenerateWindow.vue
+++ b/packages/client/src/components/MkTokenGenerateWindow.vue
@@ -11,7 +11,7 @@
 		@closed="$emit('closed')"
 		@ok="ok()"
 	>
-		<template #header>{{ title || i18n.ts.generateAccessToken }}</template>
+		<template #header>{{ title ?? i18n.ts.generateAccessToken }}</template>
 		<div v-if="information" class="_section">
 			<MkInfo warn>{{ information }}</MkInfo>
 		</div>
@@ -32,7 +32,7 @@
 				i18n.ts.enableAll
 			}}</MkButton>
 			<MkSwitch
-				v-for="kind in initialPermissions || kinds"
+				v-for="kind in initialPermissions ?? kinds"
 				:key="kind"
 				v-model="permissions[kind]"
 				style="margin-bottom: 6px"
diff --git a/packages/client/src/components/MkTutorialDialog.vue b/packages/client/src/components/MkTutorialDialog.vue
index 0253c943c..78261bae8 100644
--- a/packages/client/src/components/MkTutorialDialog.vue
+++ b/packages/client/src/components/MkTutorialDialog.vue
@@ -242,7 +242,7 @@ const dialog = ref<InstanceType<typeof XModalWindow>>();
 
 const tutorial = computed({
 	get() {
-		return defaultStore.reactiveState.tutorial.value || 0;
+		return defaultStore.reactiveState.tutorial.value ?? 0;
 	},
 	set(value) {
 		defaultStore.set("tutorial", value);
diff --git a/packages/client/src/components/MkUrlPreview.vue b/packages/client/src/components/MkUrlPreview.vue
index 89a232e21..0d8dbaef5 100644
--- a/packages/client/src/components/MkUrlPreview.vue
+++ b/packages/client/src/components/MkUrlPreview.vue
@@ -13,7 +13,7 @@
 				:target="target"
 				:title="url"
 				:class="{
-					hasButton: tweetId || player.url,
+					hasButton: tweetId ?? player.url,
 				}"
 			>
 				<div v-if="thumbnail" class="thumbnail">
@@ -51,10 +51,10 @@
 					<MkLoading mini />
 				</div>
 				<div v-else>
-					<h3 :title="title || undefined">{{ title || url }}</h3>
-					<p :title="description">
+					<h3 :title="title ?? undefined">{{ title ?? url }}</h3>
+					<p :title="description ?? undefined">
 						<span>
-							<span :title="sitename || undefined">
+							<span :title="sitename ?? undefined">
 								<img v-if="icon" class="icon" :src="icon" />
 								{{ sitename }}
 							</span>
@@ -72,7 +72,7 @@
 						: '?autoplay=1&auto_play=1')
 				"
 				:style="`aspect-ratio: ${
-					(player.width || 1) / (player.height || 1)
+					(player.width ?? 1) / (player.height ?? 1)
 				}`"
 				frameborder="0"
 				allow="autoplay; encrypted-media"
@@ -153,7 +153,7 @@ if (
 	requestUrl.hostname = "www.youtube.com";
 }
 
-const requestLang = (lang || "ja-JP").replace("ja-KS", "ja-JP");
+const requestLang = (lang ?? "ja-JP").replace("ja-KS", "ja-JP");
 
 requestUrl.hash = "";
 
diff --git a/packages/client/src/components/global/MkAcct.vue b/packages/client/src/components/global/MkAcct.vue
index bb9e231f4..ee1b1bf94 100644
--- a/packages/client/src/components/global/MkAcct.vue
+++ b/packages/client/src/components/global/MkAcct.vue
@@ -4,7 +4,7 @@
 		<span
 			v-if="user.host || detail || defaultStore.state.showFullAcct"
 			class="host"
-			>@{{ user.host || host }}</span
+			>@{{ user.host ?? host }}</span
 		>
 	</span>
 </template>
diff --git a/packages/client/src/components/global/MkUserName.vue b/packages/client/src/components/global/MkUserName.vue
index 28ce470fd..89af41fcf 100644
--- a/packages/client/src/components/global/MkUserName.vue
+++ b/packages/client/src/components/global/MkUserName.vue
@@ -2,7 +2,7 @@
 	<Mfm
 		v-if="show"
 		:class="$style.root"
-		:text="user.name || user.username"
+		:text="user.name ?? user.username"
 		:plain="true"
 		:nowrap="nowrap"
 		:custom-emojis="user.emojis"
diff --git a/packages/client/src/components/mfm.ts b/packages/client/src/components/mfm.ts
index 4f4ecd2bd..5758e70e3 100644
--- a/packages/client/src/components/mfm.ts
+++ b/packages/client/src/components/mfm.ts
@@ -113,31 +113,31 @@ export default defineComponent({
 							let style: string;
 							switch (token.props.name) {
 								case "tada": {
-									const speed = validTime(token.props.args.speed) || "1s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
-									// const ease = validEase(token.props.args.ease) || "linear";
+									const speed = validTime(token.props.args.speed) ?? "1s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
+									// const ease = validEase(token.props.args.ease) ?? "linear";
 									style = `font-size: 150%; animation: tada ${speed} ${delay} linear ${loop} both;`;
 									break;
 								}
 								case "jelly": {
-									const speed = validTime(token.props.args.speed) || "1s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "1s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-rubberBand ${speed} ${delay} linear ${loop} both;`;
 									break;
 								}
 								case "twitch": {
-									const speed = validTime(token.props.args.speed) || "0.5s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "0.5s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-twitch ${speed} ${delay} ease ${loop};`;
 									break;
 								}
 								case "shake": {
-									const speed = validTime(token.props.args.speed) || "0.5s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "0.5s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-shake ${speed} ${delay} ease ${loop};`;
 									break;
 								}
@@ -152,30 +152,30 @@ export default defineComponent({
 										: token.props.args.y
 										  ? "mfm-spinY"
 										  : "mfm-spin";
-									const speed = validTime(token.props.args.speed) || "1.5s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "1.5s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: ${anime} ${speed} ${delay} linear ${loop}; animation-direction: ${direction};`;
 									break;
 								}
 								case "jump": {
-									const speed = validTime(token.props.args.speed) || "0.75s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "0.75s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-jump ${speed} ${delay} linear ${loop};`;
 									break;
 								}
 								case "bounce": {
-									const speed = validTime(token.props.args.speed) || "0.75s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "0.75s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-bounce ${speed} ${delay} linear ${loop}; transform-origin: center bottom;`;
 									break;
 								}
 								case "rainbow": {
-									const speed = validTime(token.props.args.speed) || "1s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "1s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-rainbow ${speed} ${delay} linear ${loop};`;
 									break;
 								}
@@ -189,9 +189,9 @@ export default defineComponent({
 									const direction = token.props.args.out
 										? "alternate-reverse"
 										: "alternate";
-									const speed = validTime(token.props.args.speed) || "1.5s";
-									const delay = validTime(token.props.args.delay) || "0s";
-									const loop = validNumber(token.props.args.loop) || "infinite";
+									const speed = validTime(token.props.args.speed) ?? "1.5s";
+									const delay = validTime(token.props.args.delay) ?? "0s";
+									const loop = validNumber(token.props.args.loop) ?? "infinite";
 									style = `animation: mfm-fade ${speed} ${delay} linear ${loop}; animation-direction: ${direction};`;
 									break;
 								}
@@ -395,7 +395,7 @@ export default defineComponent({
 										this.author &&
 										this.author.host != null
 											? this.author.host
-											: token.props.host) || host,
+											: token.props.host) ?? host,
 									username: token.props.username,
 								}),
 							];
diff --git a/packages/client/src/components/page/page.counter.vue b/packages/client/src/components/page/page.counter.vue
index bd3338c2f..b4f8dee73 100644
--- a/packages/client/src/components/page/page.counter.vue
+++ b/packages/client/src/components/page/page.counter.vue
@@ -35,7 +35,7 @@ export default defineComponent({
 		function click() {
 			props.hpml.updatePageVar(
 				props.block.name,
-				value.value + (props.block.inc || 1),
+				value.value + (props.block.inc ?? 1),
 			);
 			props.hpml.eval();
 		}
diff --git a/packages/client/src/directives/size.ts b/packages/client/src/directives/size.ts
index 573027108..5c0268e99 100644
--- a/packages/client/src/directives/size.ts
+++ b/packages/client/src/directives/size.ts
@@ -58,7 +58,7 @@ function calc(el: Element) {
 	const info = mountings.get(el);
 	const width = el.clientWidth;
 
-	if (!info || info.previousWidth === width) return;
+	if (info == null || info.previousWidth === width) return;
 
 	// アクティベート前などでsrcが描画されていない場合
 	if (!width) {
diff --git a/packages/client/src/filters/user.ts b/packages/client/src/filters/user.ts
index 08b5e3be5..86a87c906 100644
--- a/packages/client/src/filters/user.ts
+++ b/packages/client/src/filters/user.ts
@@ -7,7 +7,7 @@ export const acct = (user: firefish.Acct) => {
 };
 
 export const userName = (user: firefish.entities.User) => {
-	return user.name || user.username;
+	return user.name ?? user.username;
 };
 
 export const userPage = (user: firefish.Acct, path?, absolute = false) => {
diff --git a/packages/client/src/init.ts b/packages/client/src/init.ts
index 0076e1f1e..c971b38c4 100644
--- a/packages/client/src/init.ts
+++ b/packages/client/src/init.ts
@@ -123,7 +123,7 @@ function checkForSplash() {
 
 	// #region Set lang attr
 	const html = document.documentElement;
-	html.setAttribute("lang", lang || "en-US");
+	html.setAttribute("lang", lang ?? "en-US");
 	html.setAttribute("dir", langmap[lang].rtl === true ? "rtl" : "ltr");
 	//#endregion
 
@@ -134,7 +134,7 @@ function checkForSplash() {
 	if (loginId) {
 		const target = getUrlWithoutLoginId(location.href);
 
-		if (!$i || $i.id !== loginId) {
+		if ($i == null || $i.id !== loginId) {
 			const account = await getAccountFromId(loginId);
 			if (account) {
 				await login(account.token, target);
@@ -437,7 +437,7 @@ function checkForSplash() {
 				if (Date.now() - lastUsedDate > 1000 * 60 * 60 * 2) {
 					toast(
 						i18n.t("welcomeBackWithName", {
-							name: $i.name || $i.username,
+							name: $i.name ?? $i.username,
 						}),
 					);
 				}
diff --git a/packages/client/src/os.ts b/packages/client/src/os.ts
index f0cb0c905..e90641b12 100644
--- a/packages/client/src/os.ts
+++ b/packages/client/src/os.ts
@@ -314,7 +314,7 @@ export function confirm(props: {
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
@@ -342,7 +342,7 @@ export function yesno(props: {
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
@@ -383,7 +383,7 @@ export function inputText(props: {
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
@@ -421,7 +421,7 @@ export function inputParagraph(props: {
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
@@ -461,7 +461,7 @@ export function inputNumber(props: {
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
@@ -553,7 +553,7 @@ export function select<C = any>(
 			},
 			{
 				done: (result) => {
-					resolve(result || { canceled: true });
+					resolve(result ?? { canceled: true });
 				},
 			},
 			"closed",
diff --git a/packages/client/src/pages/about.emojis.vue b/packages/client/src/pages/about.emojis.vue
index 6a33651d5..24bd4cf58 100644
--- a/packages/client/src/pages/about.emojis.vue
+++ b/packages/client/src/pages/about.emojis.vue
@@ -31,7 +31,7 @@
 			:key="category"
 			class="emojis"
 		>
-			<template #header>{{ category || i18n.ts.other }}</template>
+			<template #header>{{ category ?? i18n.ts.other }}</template>
 			<div class="zuvgdzyt">
 				<XEmoji
 					v-for="emoji in customEmojis.filter(
diff --git a/packages/client/src/pages/about.vue b/packages/client/src/pages/about.vue
index 16c6f610a..92675b4fc 100644
--- a/packages/client/src/pages/about.vue
+++ b/packages/client/src/pages/about.vue
@@ -41,7 +41,7 @@
 									@click="easterEgg"
 								/>
 								<div class="name">
-									<b>{{ $instance.name || host }}</b>
+									<b>{{ $instance.name ?? host }}</b>
 								</div>
 							</div>
 						</div>
@@ -99,7 +99,7 @@
 								></template>
 								{{
 									i18n.t("_aboutFirefish.donateHost", {
-										host: $instance.name || host,
+										host: $instance.name ?? host,
 									})
 								}}
 								<template #suffix>Donate</template>
@@ -209,7 +209,7 @@ withDefaults(
 const stats = ref(null);
 const instanceIcon = ref<HTMLImageElement>();
 let iconClicks = 0;
-const iconSrc = ref(instance.iconUrl || instance.faviconUrl || "/favicon.ico");
+const iconSrc = ref(instance.faviconUrl ?? instance.iconUrl ?? "/favicon.ico");
 const instanceIconAnimation = ref("");
 const tabs = ["overview", "emojis", "charts"];
 const tab = ref(tabs[0]);
@@ -276,8 +276,8 @@ function easterEgg() {
 			setTimeout(() => {
 				if (iconClicks % 6 === 0) {
 					iconSrc.value =
-						instance.iconUrl ||
-						instance.faviconUrl ||
+						instance.faviconUrl ??
+						instance.iconUrl ??
 						"/favicon.ico";
 				} else {
 					iconSrc.value = "/static-assets/woozy.png";
diff --git a/packages/client/src/pages/admin/_header_.vue b/packages/client/src/pages/admin/_header_.vue
index bdd1ae8c7..fe28ab871 100644
--- a/packages/client/src/pages/admin/_header_.vue
+++ b/packages/client/src/pages/admin/_header_.vue
@@ -148,7 +148,7 @@ function onTabClick(tab: Tab, ev: MouseEvent): void {
 }
 
 const calcBg = () => {
-	const rawBg = metadata?.bg || "var(--bg)";
+	const rawBg = metadata?.bg ?? "var(--bg)";
 	const tinyBg = tinycolor(
 		rawBg.startsWith("var(")
 			? getComputedStyle(document.documentElement).getPropertyValue(
diff --git a/packages/client/src/pages/admin/bot-protection.vue b/packages/client/src/pages/admin/bot-protection.vue
index 766fdc008..85cd9edb4 100644
--- a/packages/client/src/pages/admin/bot-protection.vue
+++ b/packages/client/src/pages/admin/bot-protection.vue
@@ -32,7 +32,7 @@
 						<MkCaptcha
 							provider="hcaptcha"
 							:sitekey="
-								hcaptchaSiteKey ||
+								hcaptchaSiteKey ??
 								'10000000-ffff-ffff-ffff-000000000001'
 							"
 						/>
diff --git a/packages/client/src/pages/admin/hashtags.vue b/packages/client/src/pages/admin/hashtags.vue
index 12e24e161..d203d2d93 100644
--- a/packages/client/src/pages/admin/hashtags.vue
+++ b/packages/client/src/pages/admin/hashtags.vue
@@ -47,7 +47,7 @@ async function init() {
 function save() {
 	os.apiWithDialog("admin/update-meta", {
 		hiddenTags:
-			hiddenTags.value.split("\n").map((h: string) => h.trim()) || [],
+			hiddenTags.value.split("\n").map((h: string) => h.trim()) ?? [],
 	}).then(() => {
 		fetchInstance();
 	});
diff --git a/packages/client/src/pages/admin/index.vue b/packages/client/src/pages/admin/index.vue
index 281b99152..53f696d9d 100644
--- a/packages/client/src/pages/admin/index.vue
+++ b/packages/client/src/pages/admin/index.vue
@@ -5,7 +5,11 @@
 				<div class="lxpfedzu">
 					<div class="banner">
 						<img
-							:src="$instance.iconUrl || '/favicon.ico'"
+							:src="
+								$instance.faviconUrl ??
+								$instance.iconUrl ??
+								'/favicon.ico'
+							"
 							alt=""
 							class="icon"
 						/>
diff --git a/packages/client/src/pages/admin/instance-block.vue b/packages/client/src/pages/admin/instance-block.vue
index fd80a1564..039f3424a 100644
--- a/packages/client/src/pages/admin/instance-block.vue
+++ b/packages/client/src/pages/admin/instance-block.vue
@@ -69,9 +69,9 @@ async function init() {
 
 function save() {
 	os.apiWithDialog("admin/update-meta", {
-		blockedHosts: blockedHosts.value.split("\n").map((h) => h.trim()) || [],
+		blockedHosts: blockedHosts.value.split("\n").map((h) => h.trim()) ?? [],
 		silencedHosts:
-			silencedHosts.value.split("\n").map((h) => h.trim()) || [],
+			silencedHosts.value.split("\n").map((h) => h.trim()) ?? [],
 	}).then(() => {
 		fetchInstance();
 	});
diff --git a/packages/client/src/pages/admin/relays.vue b/packages/client/src/pages/admin/relays.vue
index b5a46f4e6..f740a9af9 100644
--- a/packages/client/src/pages/admin/relays.vue
+++ b/packages/client/src/pages/admin/relays.vue
@@ -66,7 +66,7 @@ async function addRelay() {
 		.catch((err: any) => {
 			os.alert({
 				type: "error",
-				text: err.message || err,
+				text: err.message ?? err,
 			});
 		});
 }
@@ -81,7 +81,7 @@ function remove(inbox: string) {
 		.catch((err: any) => {
 			os.alert({
 				type: "error",
-				text: err.message || err,
+				text: err.message ?? err,
 			});
 		});
 }
diff --git a/packages/client/src/pages/auth.vue b/packages/client/src/pages/auth.vue
index 74b2a8cb5..11f3f05e3 100644
--- a/packages/client/src/pages/auth.vue
+++ b/packages/client/src/pages/auth.vue
@@ -126,7 +126,7 @@ const accepted = () => {
 		} else {
 			location.href = `${session.value.app.callbackUrl}?token=${
 				session.value.token
-			}&code=${session.value.token}&state=${getUrlParams().state || ""}`;
+			}&code=${session.value.token}&state=${getUrlParams().state ?? ""}`;
 		}
 	}
 };
diff --git a/packages/client/src/pages/emojis.emoji.vue b/packages/client/src/pages/emojis.emoji.vue
index 574f8fdf6..bd7e773b6 100644
--- a/packages/client/src/pages/emojis.emoji.vue
+++ b/packages/client/src/pages/emojis.emoji.vue
@@ -41,7 +41,7 @@ function menu(ev) {
 						(res) => {
 							os.alert({
 								type: "info",
-								text: `${res.license || i18n.ts.notSet}`,
+								text: `${res.license ?? i18n.ts.notSet}`,
 							});
 						},
 					);
diff --git a/packages/client/src/pages/follow.vue b/packages/client/src/pages/follow.vue
index fb771fad5..1d2dd58d3 100644
--- a/packages/client/src/pages/follow.vue
+++ b/packages/client/src/pages/follow.vue
@@ -11,7 +11,7 @@ import { i18n } from "@/i18n";
 async function follow(user): Promise<void> {
 	const { canceled } = await os.confirm({
 		type: "question",
-		text: i18n.t("followConfirm", { name: user.name || user.username }),
+		text: i18n.t("followConfirm", { name: user.name ?? user.username }),
 	});
 
 	if (canceled) {
diff --git a/packages/client/src/pages/gallery/post.vue b/packages/client/src/pages/gallery/post.vue
index 69443f1e4..37e25e0ad 100644
--- a/packages/client/src/pages/gallery/post.vue
+++ b/packages/client/src/pages/gallery/post.vue
@@ -105,7 +105,7 @@
 									<MkAcct :user="post.user" />
 								</div>
 								<MkFollowButton
-									v-if="!$i || $i.id != post.user.id"
+									v-if="!isSignedIn || $i.id !== post.user.id"
 									:user="post.user"
 									:inline="true"
 									:transparent="false"
@@ -163,7 +163,7 @@ import { definePageMetadata } from "@/scripts/page-metadata";
 import { shareAvailable } from "@/scripts/share-available";
 import { defaultStore } from "@/store";
 import icon from "@/scripts/icon";
-import { isSignedIn } from "@/reactiveAccount";
+import { $i, isSignedIn } from "@/reactiveAccount";
 
 const router = useRouter();
 
diff --git a/packages/client/src/pages/instance-info.vue b/packages/client/src/pages/instance-info.vue
index 8bbf63101..bf4637a23 100644
--- a/packages/client/src/pages/instance-info.vue
+++ b/packages/client/src/pages/instance-info.vue
@@ -33,7 +33,7 @@
 						<div class="fnfelxur">
 							<img :src="faviconUrl" alt="" class="icon" />
 							<span class="name">{{
-								instance.name || `(${i18n.ts.unknown})`
+								instance.name ?? `(${i18n.ts.unknown})`
 							}}</span>
 						</div>
 						<MkKeyValue :copy="host" oneline style="margin: 1em 0">
@@ -51,12 +51,12 @@
 							<template #value
 								><span class="_monospace"
 									>{{
-										instance.softwareName ||
+										instance.softwareName ??
 										`(${i18n.ts.unknown})`
 									}}
 									/
 									{{
-										instance.softwareVersion ||
+										instance.softwareVersion ??
 										`(${i18n.ts.unknown})`
 									}}</span
 								></template
@@ -68,11 +68,11 @@
 							}}</template>
 							<template #value
 								>{{
-									instance.maintainerName ||
+									instance.maintainerName ??
 									`(${i18n.ts.unknown})`
 								}}
 								({{
-									instance.maintainerEmail ||
+									instance.maintainerEmail ??
 									`(${i18n.ts.unknown})`
 								}})</template
 							>
diff --git a/packages/client/src/pages/messaging/messaging-room.form.vue b/packages/client/src/pages/messaging/messaging-room.form.vue
index da5fff785..7e33ef164 100644
--- a/packages/client/src/pages/messaging/messaging-room.form.vue
+++ b/packages/client/src/pages/messaging/messaging-room.form.vue
@@ -238,7 +238,7 @@ function clear() {
 }
 
 function saveDraft() {
-	const drafts = JSON.parse(localStorage.getItem("message_drafts") || "{}");
+	const drafts = JSON.parse(localStorage.getItem("message_drafts") ?? "{}");
 
 	drafts[draftKey.value] = {
 		updatedAt: new Date(),
@@ -252,7 +252,7 @@ function saveDraft() {
 }
 
 function deleteDraft() {
-	const drafts = JSON.parse(localStorage.getItem("message_drafts") || "{}");
+	const drafts = JSON.parse(localStorage.getItem("message_drafts") ?? "{}");
 
 	delete drafts[draftKey.value];
 
@@ -270,7 +270,7 @@ onMounted(() => {
 	new Autocomplete(textEl.value, text);
 
 	// 書きかけの投稿を復元
-	const draft = JSON.parse(localStorage.getItem("message_drafts") || "{}")[
+	const draft = JSON.parse(localStorage.getItem("message_drafts") ?? "{}")[
 		draftKey.value
 	];
 	if (draft) {
diff --git a/packages/client/src/pages/messaging/messaging-room.vue b/packages/client/src/pages/messaging/messaging-room.vue
index b3b20da4c..cf2bea168 100644
--- a/packages/client/src/pages/messaging/messaging-room.vue
+++ b/packages/client/src/pages/messaging/messaging-room.vue
@@ -11,7 +11,7 @@
 					<MkPagination
 						v-if="pagination"
 						ref="pagingComponent"
-						:key="userAcct || groupId"
+						:key="userAcct ?? groupId"
 						:pagination="pagination"
 					>
 						<template #empty>
@@ -162,7 +162,7 @@ async function fetch() {
 		const acct = Acct.parse(props.userAcct);
 		user.value = await os.api("users/show", {
 			username: acct.username,
-			host: acct.host || undefined,
+			host: acct.host ?? undefined,
 		});
 		group.value = null;
 
diff --git a/packages/client/src/pages/note.vue b/packages/client/src/pages/note.vue
index ca120fca4..008b923a0 100644
--- a/packages/client/src/pages/note.vue
+++ b/packages/client/src/pages/note.vue
@@ -181,7 +181,7 @@ definePageMetadata(
 							? ""
 							: i18n.t("noteOf", {
 									user:
-										appearNote.value.user.name ||
+										appearNote.value.user.name ??
 										appearNote.value.user.username,
 								}),
 					subtitle: new Date(
@@ -192,7 +192,7 @@ definePageMetadata(
 					share: {
 						title: i18n.t("noteOf", {
 							user:
-								appearNote.value.user.name ||
+								appearNote.value.user.name ??
 								appearNote.value.user.username,
 						}),
 						text: appearNote.value.text,
diff --git a/packages/client/src/pages/page.vue b/packages/client/src/pages/page.vue
index 4ee839af5..c8425d791 100644
--- a/packages/client/src/pages/page.vue
+++ b/packages/client/src/pages/page.vue
@@ -150,7 +150,7 @@
 									<MkAcct :user="page.user" />
 								</div>
 								<MkFollowButton
-									v-if="!$i || $i.id != page.user.id"
+									v-if="!isSignedIn || $i.id !== page.user.id"
 									:user="page.user"
 									:inline="true"
 									:transparent="false"
@@ -215,7 +215,7 @@ import { definePageMetadata } from "@/scripts/page-metadata";
 import { shareAvailable } from "@/scripts/share-available";
 import { defaultStore } from "@/store";
 import icon from "@/scripts/icon";
-import { isSignedIn } from "@/reactiveAccount";
+import { $i, isSignedIn } from "@/reactiveAccount";
 
 const props = defineProps<{
 	pageName: string;
@@ -272,7 +272,7 @@ function share() {
 
 function shareWithNote() {
 	os.post({
-		initialText: `${page.value.title || page.value.name} ${url}/@${
+		initialText: `${page.value.title ?? page.value.name} ${url}/@${
 			page.value.user.username
 		}/pages/${page.value.name}`,
 	});
@@ -312,11 +312,11 @@ definePageMetadata(
 	computed(() =>
 		page.value
 			? {
-					title: computed(() => page.value.title || page.value.name),
+					title: computed(() => page.value.title ?? page.value.name),
 					avatar: page.value.user,
 					path: `/@${page.value.user.username}/pages/${page.value.name}`,
 					share: {
-						title: page.value.title || page.value.name,
+						title: page.value.title ?? page.value.name,
 						text: page.value.summary,
 					},
 				}
diff --git a/packages/client/src/pages/settings/notifications.vue b/packages/client/src/pages/settings/notifications.vue
index 010045189..84b2ece19 100644
--- a/packages/client/src/pages/settings/notifications.vue
+++ b/packages/client/src/pages/settings/notifications.vue
@@ -66,7 +66,7 @@ const pushRegistrationInServer = computed(
 	() => allowButton.value?.pushRegistrationInServer,
 );
 const sendReadMessage = computed(
-	() => pushRegistrationInServer.value?.sendReadMessage || false,
+	() => pushRegistrationInServer.value?.sendReadMessage ?? false,
 );
 
 async function readAllUnreadNotes() {
diff --git a/packages/client/src/pages/settings/preferences-backups.vue b/packages/client/src/pages/settings/preferences-backups.vue
index bb6c852e3..460955974 100644
--- a/packages/client/src/pages/settings/preferences-backups.vue
+++ b/packages/client/src/pages/settings/preferences-backups.vue
@@ -169,7 +169,7 @@ const connection = isSignedIn && stream.useChannel("main");
 const profiles = ref<Record<string, Profile> | null>(null);
 
 os.api("i/registry/get-all", { scope }).then((res) => {
-	profiles.value = res || {};
+	profiles.value = res ?? {};
 });
 
 function isObject(value: unknown): value is Record<string, unknown> {
diff --git a/packages/client/src/pages/settings/sounds.vue b/packages/client/src/pages/settings/sounds.vue
index 084e16b4c..bb9a602e3 100644
--- a/packages/client/src/pages/settings/sounds.vue
+++ b/packages/client/src/pages/settings/sounds.vue
@@ -21,7 +21,7 @@
 				>
 					{{ i18n.t("_sfx." + type) }}
 					<template #suffix>{{
-						sounds[type].type || i18n.ts.none
+						sounds[type].type ?? i18n.ts.none
 					}}</template>
 					<template #suffixIcon
 						><i :class="icon('ph-caret-down')"></i
diff --git a/packages/client/src/pages/settings/webhook.vue b/packages/client/src/pages/settings/webhook.vue
index 7204e4c5e..aab9723c6 100644
--- a/packages/client/src/pages/settings/webhook.vue
+++ b/packages/client/src/pages/settings/webhook.vue
@@ -37,7 +37,7 @@
 								:style="{ color: 'var(--error)' }"
 							></i>
 						</template>
-						{{ webhook.name || webhook.url }}
+						{{ webhook.name ?? webhook.url }}
 						<template #suffix>
 							<MkTime
 								v-if="webhook.latestSentAt"
diff --git a/packages/client/src/pages/user/home.vue b/packages/client/src/pages/user/home.vue
index 0acc12f95..63e2fec98 100644
--- a/packages/client/src/pages/user/home.vue
+++ b/packages/client/src/pages/user/home.vue
@@ -108,7 +108,7 @@
 										v-if="
 											patrons?.includes(
 												`@${user.username}@${
-													user.host || host
+													user.host ?? host
 												}`,
 											)
 										"
@@ -197,7 +197,7 @@
 									v-if="
 										patrons?.includes(
 											`@${user.username}@${
-												user.host || host
+												user.host ?? host
 											}`,
 										)
 									"
diff --git a/packages/client/src/pages/welcome.entrance.a.vue b/packages/client/src/pages/welcome.entrance.a.vue
index cd6e64857..8f9991bbf 100644
--- a/packages/client/src/pages/welcome.entrance.a.vue
+++ b/packages/client/src/pages/welcome.entrance.a.vue
@@ -17,8 +17,8 @@
 			<div class="main">
 				<img
 					:src="
-						instance.iconUrl ||
-						instance.faviconUrl ||
+						instance.faviconUrl ??
+						instance.iconUrl ??
 						'/favicon.ico'
 					"
 					alt=""
@@ -41,7 +41,7 @@
 						<div
 							class="desc"
 							v-html="
-								meta.description || i18n.ts.headlineFirefish
+								meta.description ?? i18n.ts.headlineFirefish
 							"
 						></div>
 					</div>
diff --git a/packages/client/src/pages/welcome.entrance.b.vue b/packages/client/src/pages/welcome.entrance.b.vue
index fd4982357..1de90ae15 100644
--- a/packages/client/src/pages/welcome.entrance.b.vue
+++ b/packages/client/src/pages/welcome.entrance.b.vue
@@ -15,7 +15,7 @@
 				<div class="about">
 					<div
 						class="desc"
-						v-html="meta.description || i18n.ts.headlineFirefish"
+						v-html="meta.description ?? i18n.ts.headlineFirefish"
 					></div>
 				</div>
 				<div class="action">
diff --git a/packages/client/src/pages/welcome.entrance.c.vue b/packages/client/src/pages/welcome.entrance.c.vue
index ff4bb3565..8399ac7bf 100644
--- a/packages/client/src/pages/welcome.entrance.c.vue
+++ b/packages/client/src/pages/welcome.entrance.c.vue
@@ -30,7 +30,7 @@
 							<div
 								class="desc"
 								v-html="
-									meta.description || i18n.ts.headlineFirefish
+									meta.description ?? i18n.ts.headlineFirefish
 								"
 							></div>
 						</div>
diff --git a/packages/client/src/pizzax.ts b/packages/client/src/pizzax.ts
index 5ee06d0b8..9d2eb74df 100644
--- a/packages/client/src/pizzax.ts
+++ b/packages/client/src/pizzax.ts
@@ -41,16 +41,16 @@ export class Storage<T extends StateDef> {
 
 		// TODO: indexedDBにする
 		const deviceState = JSON.parse(
-			localStorage.getItem(this.keyForLocalStorage) || "{}",
+			localStorage.getItem(this.keyForLocalStorage) ?? "{}",
 		);
 		const deviceAccountState = isSignedIn
 			? JSON.parse(
-					localStorage.getItem(`${this.keyForLocalStorage}::${$i.id}`) || "{}",
+					localStorage.getItem(`${this.keyForLocalStorage}::${$i.id}`) ?? "{}",
 			  )
 			: {};
 		const registryCache = isSignedIn
 			? JSON.parse(
-					localStorage.getItem(`${this.keyForLocalStorage}::cache::${$i.id}`) ||
+					localStorage.getItem(`${this.keyForLocalStorage}::cache::${$i.id}`) ??
 						"{}",
 			  )
 			: {};
@@ -136,7 +136,7 @@ export class Storage<T extends StateDef> {
 					const cache = JSON.parse(
 						localStorage.getItem(
 							`${this.keyForLocalStorage}::cache::${$i.id}`,
-						) || "{}",
+						) ?? "{}",
 					);
 					if (cache[key] !== value) {
 						cache[key] = value;
@@ -159,7 +159,7 @@ export class Storage<T extends StateDef> {
 		switch (this.def[key].where) {
 			case "device": {
 				const deviceState = JSON.parse(
-					localStorage.getItem(this.keyForLocalStorage) || "{}",
+					localStorage.getItem(this.keyForLocalStorage) ?? "{}",
 				);
 				deviceState[key] = value;
 				localStorage.setItem(
@@ -171,7 +171,7 @@ export class Storage<T extends StateDef> {
 			case "deviceAccount": {
 				if (!isSignedIn) break;
 				const deviceAccountState = JSON.parse(
-					localStorage.getItem(`${this.keyForLocalStorage}::${$i.id}`) || "{}",
+					localStorage.getItem(`${this.keyForLocalStorage}::${$i.id}`) ?? "{}",
 				);
 				deviceAccountState[key] = value;
 				localStorage.setItem(
@@ -183,7 +183,7 @@ export class Storage<T extends StateDef> {
 			case "account": {
 				if (!isSignedIn) break;
 				const cache = JSON.parse(
-					localStorage.getItem(`${this.keyForLocalStorage}::cache::${$i.id}`) ||
+					localStorage.getItem(`${this.keyForLocalStorage}::cache::${$i.id}`) ??
 						"{}",
 				);
 				cache[key] = value;
diff --git a/packages/client/src/plugin.ts b/packages/client/src/plugin.ts
index 2fceb20df..933333fb9 100644
--- a/packages/client/src/plugin.ts
+++ b/packages/client/src/plugin.ts
@@ -143,7 +143,7 @@ function registerPostFormAction({ pluginId, title, handler }) {
 			pluginContext.execFn(handler, [
 				utils.jsToVal(form),
 				values.FN_NATIVE(([key, value]) => {
-					if (!key || !value) {
+					if (key == null || value == null) {
 						return;
 					}
 					update(utils.valToJs(key), utils.valToJs(value));
diff --git a/packages/client/src/reactiveAccount.ts b/packages/client/src/reactiveAccount.ts
index c32b6df11..6b5fbc5c1 100644
--- a/packages/client/src/reactiveAccount.ts
+++ b/packages/client/src/reactiveAccount.ts
@@ -9,6 +9,6 @@ export const $i = accountData
 	: null;
 
 export const isSignedIn = $i != null;
-export const isModerator = isSignedIn && ($i.isModerator || $i.isAdmin);
-export const isAdmin = isSignedIn && $i.isAdmin;
-export const isEmojiMod = isSignedIn && $i.emojiModPerm !== "unauthorized";
+export const isModerator = $i != null && ($i.isModerator || $i.isAdmin);
+export const isAdmin = $i?.isAdmin;
+export const isEmojiMod = $i != null && $i?.emojiModPerm !== "unauthorized";
diff --git a/packages/client/src/scripts/aiscript/api.ts b/packages/client/src/scripts/aiscript/api.ts
index d6beee58f..3f790848e 100644
--- a/packages/client/src/scripts/aiscript/api.ts
+++ b/packages/client/src/scripts/aiscript/api.ts
@@ -34,7 +34,7 @@ export function createAiScriptEnv(opts) {
 			const res = await os.api(
 				ep.value,
 				utils.valToJs(param),
-				token ? token.value : opts.token || null,
+				token ? token.value : opts.token ?? null,
 			);
 			return utils.jsToVal(res);
 		}),
diff --git a/packages/client/src/scripts/check-word-mute.ts b/packages/client/src/scripts/check-word-mute.ts
index acdaf4389..9dd38cc42 100644
--- a/packages/client/src/scripts/check-word-mute.ts
+++ b/packages/client/src/scripts/check-word-mute.ts
@@ -15,7 +15,7 @@ function checkLangMute(
 	const mutedLangList = new Set(mutedLangs.flatMap((e) => e));
 	// handle subtags
 	// e.g. if lang = "zh-hant-tw", check ["zh", "zh-hant", "zh-hant-tw"]
-	const langChunks: string[] = (note.lang || "").split("-");
+	const langChunks: string[] = (note.lang ?? "").split("-");
 	for (let i = 0; i < langChunks.length; i++) {
 		const lang = langChunks.slice(0, i + 1).join("-");
 		if (mutedLangList.has(lang)) {
diff --git a/packages/client/src/scripts/chiptune2.ts b/packages/client/src/scripts/chiptune2.ts
index 5904f37fc..1992e70b4 100644
--- a/packages/client/src/scripts/chiptune2.ts
+++ b/packages/client/src/scripts/chiptune2.ts
@@ -12,7 +12,7 @@ ChiptuneJsConfig.prototype.constructor = ChiptuneJsConfig;
 export function ChiptuneJsPlayer(config: object) {
 	this.libopenmpt = null;
 	this.config = config;
-	this.audioContext = config.context || new ChiptuneAudioContext();
+	this.audioContext = config.context ?? new ChiptuneAudioContext();
 	this.context = this.audioContext.createGain();
 	this.currentPlayingNode = null;
 	this.handlers = [];
@@ -157,7 +157,7 @@ ChiptuneJsPlayer.prototype.play = async function (buffer: ArrayBuffer) {
 		}
 		this.libopenmpt._openmpt_module_set_repeat_count(
 			processNode.modulePtr,
-			this.config.repeatCount || 0,
+			this.config.repeatCount ?? 0,
 		);
 		this.currentPlayingNode = processNode;
 		processNode.connect(this.context);
diff --git a/packages/client/src/scripts/collect-page-vars.ts b/packages/client/src/scripts/collect-page-vars.ts
index e7d4a6d0e..11a764383 100644
--- a/packages/client/src/scripts/collect-page-vars.ts
+++ b/packages/client/src/scripts/collect-page-vars.ts
@@ -6,19 +6,19 @@ export function collectPageVars(content) {
 				pageVars.push({
 					name: x.name,
 					type: "string",
-					value: x.default || "",
+					value: x.default ?? "",
 				});
 			} else if (x.type === "textareaInput") {
 				pageVars.push({
 					name: x.name,
 					type: "string",
-					value: x.default || "",
+					value: x.default ?? "",
 				});
 			} else if (x.type === "numberInput") {
 				pageVars.push({
 					name: x.name,
 					type: "number",
-					value: x.default || 0,
+					value: x.default ?? 0,
 				});
 			} else if (x.type === "switch") {
 				pageVars.push({
@@ -36,7 +36,7 @@ export function collectPageVars(content) {
 				pageVars.push({
 					name: x.name,
 					type: "string",
-					value: x.default || "",
+					value: x.default ?? "",
 				});
 			} else if (x.children) {
 				collect(x.children);
diff --git a/packages/client/src/scripts/emojilist.ts b/packages/client/src/scripts/emojilist.ts
index 39d000b34..a167a30ad 100644
--- a/packages/client/src/scripts/emojilist.ts
+++ b/packages/client/src/scripts/emojilist.ts
@@ -37,7 +37,7 @@ export const categoryMapping = {
 } as const;
 
 export function addSkinTone(emoji: string, skinTone?: number) {
-	const chosenSkinTone = skinTone || defaultStore.state.reactionPickerSkinTone;
+	const chosenSkinTone = skinTone ?? defaultStore.state.reactionPickerSkinTone;
 	const skinToneModifiers = [
 		"",
 		emojiComponents.light_skin_tone,
@@ -51,7 +51,7 @@ export function addSkinTone(emoji: string, skinTone?: number) {
 		"",
 	);
 	if (individualData[strippedEmoji].skin_tone_support) {
-		return strippedEmoji + (skinToneModifiers[chosenSkinTone - 1] || "");
+		return strippedEmoji + (skinToneModifiers[chosenSkinTone - 1] ?? "");
 	} else {
 		return emoji;
 	}
@@ -62,7 +62,7 @@ const newData = {};
 for (const originalCategory of Object.keys(data)) {
 	const newCategory = categoryMapping[originalCategory];
 	if (newCategory) {
-		newData[newCategory] = newData[newCategory] || [];
+		newData[newCategory] = newData[newCategory] ?? [];
 		for (const emojiIndex of Object.keys(data[originalCategory])) {
 			const emojiObj = { ...data[originalCategory][emojiIndex] };
 			emojiObj.category = newCategory;
@@ -79,8 +79,8 @@ export const emojilist: UnicodeEmojiDef[] = Object.keys(newData).reduce(
 				emoji: item.emoji,
 				slug: item.slug,
 				category: item.category,
-				skin_tone_support: item.skin_tone_support || false,
-				keywords: item.keywords || [],
+				skin_tone_support: item.skin_tone_support ?? false,
+				keywords: item.keywords ?? [],
 			};
 		});
 		return acc.concat(categoryItems);
@@ -92,6 +92,6 @@ export function getNicelyLabeledCategory(internalName) {
 	return (
 		Object.keys(categoryMapping).find(
 			(key) => categoryMapping[key] === internalName,
-		) || internalName
+		) ?? internalName
 	);
 }
diff --git a/packages/client/src/scripts/format-time-string.ts b/packages/client/src/scripts/format-time-string.ts
index 5a840bc78..d6491bb27 100644
--- a/packages/client/src/scripts/format-time-string.ts
+++ b/packages/client/src/scripts/format-time-string.ts
@@ -28,7 +28,7 @@ function formatLocaleString(date: Date, format: string): string {
 				].includes(kind)
 			) {
 				return date.toLocaleString(window.navigator.language, {
-					[kind]: option || defaultLocaleStringFormats[kind],
+					[kind]: option ?? defaultLocaleStringFormats[kind],
 				});
 			} else {
 				return match;
@@ -55,8 +55,14 @@ export function formatDateTimeString(date: Date, format: string): string {
 		.replace(/d/g, date.getDate().toString())
 		.replace(/HH/g, `0${date.getHours()}`.slice(-2))
 		.replace(/H/g, date.getHours().toString())
-		.replace(/hh/g, `0${date.getHours() % 12 || 12}`.slice(-2))
-		.replace(/h/g, (date.getHours() % 12 || 12).toString())
+		.replace(
+			/hh/g,
+			`0${date.getHours() % 12 === 0 ? 12 : date.getHours() % 12}`.slice(-2),
+		)
+		.replace(
+			/h/g,
+			(date.getHours() % 12 === 0 ? 12 : date.getHours() % 12).toString(),
+		)
 		.replace(/mm/g, `0${date.getMinutes()}`.slice(-2))
 		.replace(/m/g, date.getMinutes().toString())
 		.replace(/ss/g, `0${date.getSeconds()}`.slice(-2))
diff --git a/packages/client/src/scripts/get-note-menu.ts b/packages/client/src/scripts/get-note-menu.ts
index 74185f7cc..966547a33 100644
--- a/packages/client/src/scripts/get-note-menu.ts
+++ b/packages/client/src/scripts/get-note-menu.ts
@@ -266,7 +266,7 @@ export function getNoteMenu(props: {
 		props.translating.value = true;
 		props.translation.value = await translate_(
 			appearNote.id,
-			translateLang || lang || navigator.language,
+			translateLang ?? lang ?? navigator.language,
 		);
 
 		// use UI language as the second translation target
@@ -274,7 +274,7 @@ export function getNoteMenu(props: {
 			translateLang != null &&
 			lang != null &&
 			translateLang !== lang &&
-			(!props.translation.value ||
+			(props.translation.value == null ||
 				props.translation.value.sourceLang.toLowerCase() ===
 					translateLang.slice(0, 2))
 		)
@@ -349,7 +349,7 @@ export function getNoteMenu(props: {
 					  },
 			),
 			isAppearAuthor
-				? ($i.pinnedNoteIds || []).includes(appearNote.id)
+				? ($i.pinnedNoteIds ?? []).includes(appearNote.id)
 					? {
 							icon: `${icon("ph-push-pin")}`,
 							text: i18n.ts.unpin,
@@ -368,12 +368,12 @@ export function getNoteMenu(props: {
 						action: translate,
 				  }
 				: undefined,
-			appearNote.url || appearNote.uri
+			appearNote.url ?? appearNote.uri
 				? {
 						icon: `${icon("ph-arrow-square-out")}`,
 						text: i18n.ts.showOnRemote,
 						action: () => {
-							window.open(appearNote.url || appearNote.uri, "_blank");
+							window.open(appearNote.url ?? appearNote.uri, "_blank");
 						},
 				  }
 				: undefined,
@@ -392,7 +392,7 @@ export function getNoteMenu(props: {
 						text: i18n.ts.copyLink,
 						action: copyLink,
 					},
-					appearNote.url || appearNote.uri
+					appearNote.url ?? appearNote.uri
 						? {
 								icon: `${icon("ph-link-simple")}`,
 								text: `${i18n.ts.copyLink} (${i18n.ts.origin})`,
@@ -425,8 +425,8 @@ export function getNoteMenu(props: {
 						text: i18n.ts.reportAbuse,
 						action: () => {
 							const u =
-								appearNote.url ||
-								appearNote.uri ||
+								appearNote.url ??
+								appearNote.uri ??
 								`${url}/notes/${appearNote.id}`;
 							os.popup(
 								defineAsyncComponent(
@@ -490,12 +490,12 @@ export function getNoteMenu(props: {
 		].filter((x) => x !== undefined);
 	} else {
 		menu = [
-			appearNote.url || appearNote.uri
+			appearNote.url ?? appearNote.uri
 				? {
 						icon: `${icon("ph-arrow-square-out")}`,
 						text: i18n.ts.showOnRemote,
 						action: () => {
-							window.open(appearNote.url || appearNote.uri, "_blank");
+							window.open(appearNote.url ?? appearNote.uri, "_blank");
 						},
 				  }
 				: undefined,
@@ -509,7 +509,7 @@ export function getNoteMenu(props: {
 				text: i18n.ts.copyLink,
 				action: copyLink,
 			},
-			appearNote.url || appearNote.uri
+			appearNote.url ?? appearNote.uri
 				? {
 						icon: `${icon("ph-link-simple")}`,
 						text: `${i18n.ts.copyLink} (${i18n.ts.origin})`,
diff --git a/packages/client/src/scripts/get-note-summary.ts b/packages/client/src/scripts/get-note-summary.ts
index 7a09c601a..2a39a3b71 100644
--- a/packages/client/src/scripts/get-note-summary.ts
+++ b/packages/client/src/scripts/get-note-summary.ts
@@ -21,7 +21,7 @@ export const getNoteSummary = (note: firefish.entities.Note): string => {
 	}
 
 	// ファイルが添付されているとき
-	if ((note.files || []).length !== 0) {
+	if ((note.files ?? []).length !== 0) {
 		const len = note.files?.length;
 		summary += ` 📎${len !== 1 ? ` (${len})` : ""}`;
 	}
diff --git a/packages/client/src/scripts/get-user-menu.ts b/packages/client/src/scripts/get-user-menu.ts
index 8fc34d791..5f1a1e8f6 100644
--- a/packages/client/src/scripts/get-user-menu.ts
+++ b/packages/client/src/scripts/get-user-menu.ts
@@ -227,14 +227,14 @@ export function getUserMenu(user, router: Router = mainRouter) {
 		{
 			type: "label",
 			text: user.host
-				? `@${user.username}@${user.host || host}`
+				? `@${user.username}@${user.host ?? host}`
 				: `@${user.username}`,
 		},
 		{
 			icon: `${icon("ph-at")}`,
 			text: i18n.ts.copyUsername,
 			action: () => {
-				copyToClipboard(`@${user.username}@${user.host || host}`);
+				copyToClipboard(`@${user.username}@${user.host ?? host}`);
 			},
 		},
 		{
diff --git a/packages/client/src/scripts/get-user-name.ts b/packages/client/src/scripts/get-user-name.ts
index 0f8916de8..9d769bb86 100644
--- a/packages/client/src/scripts/get-user-name.ts
+++ b/packages/client/src/scripts/get-user-name.ts
@@ -2,5 +2,5 @@ export default function (user: {
 	name?: string | null;
 	username: string;
 }): string {
-	return user.name || user.username;
+	return user.name ?? user.username;
 }
diff --git a/packages/client/src/scripts/hpml/evaluator.ts b/packages/client/src/scripts/hpml/evaluator.ts
index 04b179eff..6185fe89f 100644
--- a/packages/client/src/scripts/hpml/evaluator.ts
+++ b/packages/client/src/scripts/hpml/evaluator.ts
@@ -79,7 +79,7 @@ export class Hpml {
 				? `${opts.url}/@${this.page.user.username}/pages/${this.page.name}`
 				: "",
 			LOGIN: opts.visitor != null,
-			NAME: opts.visitor ? opts.visitor.name || opts.visitor.username : "",
+			NAME: opts.visitor ? opts.visitor.name ?? opts.visitor.username : "",
 			USERNAME: opts.visitor ? opts.visitor.username : "",
 			USERID: opts.visitor ? opts.visitor.id : "",
 			NOTES_COUNT: opts.visitor ? opts.visitor.notesCount : 0,
@@ -187,11 +187,11 @@ export class Hpml {
 			}
 
 			if (expr.type === "text" || expr.type === "multiLineText") {
-				return this._interpolateScope(expr.value || "", scope);
+				return this._interpolateScope(expr.value ?? "", scope);
 			}
 
 			if (expr.type === "textList") {
-				return this._interpolateScope(expr.value || "", scope)
+				return this._interpolateScope(expr.value ?? "", scope)
 					.trim()
 					.split("\n");
 			}
diff --git a/packages/client/src/scripts/hpml/index.ts b/packages/client/src/scripts/hpml/index.ts
index 224ad29a4..a780d5ee2 100644
--- a/packages/client/src/scripts/hpml/index.ts
+++ b/packages/client/src/scripts/hpml/index.ts
@@ -103,7 +103,7 @@ export class HpmlScope {
 		name?: HpmlScope["name"],
 	) {
 		this.layerdStates = layerdStates;
-		this.name = name || "anonymous";
+		this.name = name ?? "anonymous";
 	}
 
 	@autobind
diff --git a/packages/client/src/scripts/hpml/lib.ts b/packages/client/src/scripts/hpml/lib.ts
index 097cc2cbf..6fe0fedee 100644
--- a/packages/client/src/scripts/hpml/lib.ts
+++ b/packages/client/src/scripts/hpml/lib.ts
@@ -504,7 +504,7 @@ export function initHpmlLib(
 		strPick: (a: string, b: number) => a[b - 1],
 		strReplace: (a: string, b: string, c: string) => a.split(b).join(c),
 		strReverse: (a: string) => a.split("").reverse().join(""),
-		join: (texts: string[], separator: string) => texts.join(separator || ""),
+		join: (texts: string[], separator: string) => texts.join(separator ?? ""),
 		stringToNumber: (a: string) => parseInt(a),
 		numberToString: (a: number) => a.toString(),
 		splitStrByLine: (a: string) => a.split("\n"),
diff --git a/packages/client/src/scripts/hpml/type-checker.ts b/packages/client/src/scripts/hpml/type-checker.ts
index 7299528d9..d7b03862b 100644
--- a/packages/client/src/scripts/hpml/type-checker.ts
+++ b/packages/client/src/scripts/hpml/type-checker.ts
@@ -30,7 +30,7 @@ export class HpmlTypeChecker {
 	public typeCheck(v: Expr): TypeError | null {
 		if (isLiteralValue(v)) return null;
 
-		const def = funcDefs[v.type || ""];
+		const def = funcDefs[v.type ?? ""];
 		if (def == null) {
 			throw new Error(`Unknown type: ${v.type}`);
 		}
@@ -66,7 +66,7 @@ export class HpmlTypeChecker {
 
 	@autobind
 	public getExpectedType(v: Expr, slot: number): Type {
-		const def = funcDefs[v.type || ""];
+		const def = funcDefs[v.type ?? ""];
 		if (def == null) {
 			throw new Error(`Unknown type: ${v.type}`);
 		}
@@ -86,7 +86,7 @@ export class HpmlTypeChecker {
 		}
 
 		if (typeof def.in[slot] === "number") {
-			return generic[def.in[slot]] || null;
+			return generic[def.in[slot]] ?? null;
 		} else {
 			return def.in[slot];
 		}
@@ -110,7 +110,7 @@ export class HpmlTypeChecker {
 				return pageVar.type;
 			}
 
-			const envVar = envVarsDef[v.value || ""];
+			const envVar = envVarsDef[v.value ?? ""];
 			if (envVar !== undefined) {
 				return envVar;
 			}
diff --git a/packages/client/src/scripts/physics.ts b/packages/client/src/scripts/physics.ts
index 5375c01d2..526628a9e 100644
--- a/packages/client/src/scripts/physics.ts
+++ b/packages/client/src/scripts/physics.ts
@@ -90,7 +90,7 @@ export function physics(container: HTMLElement) {
 				objEl.offsetHeight,
 				{
 					chamfer: {
-						radius: parseInt(style.borderRadius || "0", 10),
+						radius: parseInt(style.borderRadius ?? "0", 10),
 					},
 					restitution: 0.5,
 				},
diff --git a/packages/client/src/scripts/scroll.ts b/packages/client/src/scripts/scroll.ts
index 0ac4cd724..e6ea2be95 100644
--- a/packages/client/src/scripts/scroll.ts
+++ b/packages/client/src/scripts/scroll.ts
@@ -36,7 +36,7 @@ export function isBottomVisible(
 }
 
 export function onScrollTop(el: Element, cb) {
-	const container = getScrollContainer(el) || window;
+	const container = getScrollContainer(el) ?? window;
 	const onScroll = (ev) => {
 		if (!document.body.contains(el)) return;
 		if (isTopVisible(el)) {
@@ -48,7 +48,7 @@ export function onScrollTop(el: Element, cb) {
 }
 
 export function onScrollBottom(el: Element, cb) {
-	const container = getScrollContainer(el) || window;
+	const container = getScrollContainer(el) ?? window;
 	const onScroll = (ev) => {
 		if (!document.body.contains(el)) return;
 		const pos = getScrollPosition(el);
diff --git a/packages/client/src/scripts/upload.ts b/packages/client/src/scripts/upload.ts
index fac327da7..6dec5cbbb 100644
--- a/packages/client/src/scripts/upload.ts
+++ b/packages/client/src/scripts/upload.ts
@@ -44,7 +44,7 @@ export function uploadFile(
 		reader.onload = async (ev) => {
 			const ctx = reactive<Uploading>({
 				id,
-				name: name || file.name || "untitled",
+				name: name ?? file.name ?? "untitled",
 				progressMax: undefined,
 				progressValue: undefined,
 				img: window.URL.createObjectURL(file),
@@ -78,7 +78,7 @@ export function uploadFile(
 
 			const formData = new FormData();
 			formData.append("force", "true");
-			formData.append("file", resizedImage || file);
+			formData.append("file", resizedImage ?? file);
 			formData.append("name", ctx.name);
 			if (folder) formData.append("folderId", folder);
 
diff --git a/packages/client/src/scripts/use-note-capture.ts b/packages/client/src/scripts/use-note-capture.ts
index 94b8068ee..d8cbe1ec0 100644
--- a/packages/client/src/scripts/use-note-capture.ts
+++ b/packages/client/src/scripts/use-note-capture.ts
@@ -24,14 +24,14 @@ export function useNoteCapture(props: {
 				const reaction = body.reaction;
 
 				if (body.emoji) {
-					const emojis = note.value.emojis || [];
+					const emojis = note.value.emojis ?? [];
 					if (!emojis.includes(body.emoji)) {
 						note.value.emojis = [...emojis, body.emoji];
 					}
 				}
 
-				// TODO: reactionsプロパティがない場合ってあったっけ？ なければ || {} は消せる
-				const currentCount = note.value.reactions?.[reaction] || 0;
+				// TODO: reactionsプロパティがない場合ってあったっけ？
+				const currentCount = note.value.reactions?.[reaction] ?? 0;
 
 				note.value.reactions[reaction] = currentCount + 1;
 
@@ -44,8 +44,8 @@ export function useNoteCapture(props: {
 			case "unreacted": {
 				const reaction = body.reaction;
 
-				// TODO: reactionsプロパティがない場合ってあったっけ？ なければ || {} は消せる
-				const currentCount = note.value.reactions?.[reaction] || 0;
+				// TODO: reactionsプロパティがない場合ってあったっけ？
+				const currentCount = note.value.reactions?.[reaction] ?? 0;
 
 				note.value.reactions[reaction] = Math.max(0, currentCount - 1);
 
diff --git a/packages/client/src/theme-store.ts b/packages/client/src/theme-store.ts
index 794502da2..010895f8a 100644
--- a/packages/client/src/theme-store.ts
+++ b/packages/client/src/theme-store.ts
@@ -5,7 +5,7 @@ import { $i, isSignedIn } from "@/reactiveAccount";
 const lsCacheKey = isSignedIn ? `themes:${$i.id}` : "";
 
 export function getThemes(): Theme[] {
-	return JSON.parse(localStorage.getItem(lsCacheKey) || "[]");
+	return JSON.parse(localStorage.getItem(lsCacheKey) ?? "[]");
 }
 
 export async function fetchThemes(): Promise<void> {
diff --git a/packages/client/src/ui/_common_/navbar.vue b/packages/client/src/ui/_common_/navbar.vue
index 34567e285..5603b2a95 100644
--- a/packages/client/src/ui/_common_/navbar.vue
+++ b/packages/client/src/ui/_common_/navbar.vue
@@ -146,7 +146,7 @@
 					></i>
 				</button>
 				<!-- <button v-click-anime v-tooltip.noDelay.right="$instance.name ?? i18n.ts.instance" class="item _button instance" @click="openInstanceMenu">
-				<img :src="$instance.iconUrl || $instance.faviconUrl || '/favicon.ico'" alt="" class="icon"/>
+				<img :src="$instance.faviconUrl ?? $instance.iconUrl ?? '/favicon.ico'" alt="" class="icon"/>
 			</button> -->
 				<!-- <button v-click-anime v-tooltip.noDelay.right="`${i18n.ts.account}: @${$i.username}`" class="item _button account" @click="openAccountMenu">
 				<MkAvatar :user="$i" class="account"/><MkAcct class="text" :user="$i"/>
diff --git a/packages/client/src/ui/_common_/upload.vue b/packages/client/src/ui/_common_/upload.vue
index 674ae27cb..966879784 100644
--- a/packages/client/src/ui/_common_/upload.vue
+++ b/packages/client/src/ui/_common_/upload.vue
@@ -41,8 +41,8 @@
 					</p>
 				</div>
 				<progress
-					:value="ctx.progressValue || 0"
-					:max="ctx.progressMax || 0"
+					:value="ctx.progressValue ?? 0"
+					:max="ctx.progressMax ?? 0"
 					:class="{
 						initing: ctx.progressValue === undefined,
 						waiting:
diff --git a/packages/client/src/ui/visitor/a.vue b/packages/client/src/ui/visitor/a.vue
index 1688b9be6..8ba831b3a 100644
--- a/packages/client/src/ui/visitor/a.vue
+++ b/packages/client/src/ui/visitor/a.vue
@@ -16,7 +16,11 @@
 				<div v-if="meta" class="about">
 					<div
 						class="desc"
-						v-html="meta.description || i18n.ts.introFirefish"
+						v-html="
+							meta.description !== ''
+								? meta.description
+								: i18n.ts.introFirefish
+						"
 					></div>
 				</div>
 				<div class="action">
diff --git a/packages/client/src/ui/visitor/b.vue b/packages/client/src/ui/visitor/b.vue
index 05b5a740b..5d55851e8 100644
--- a/packages/client/src/ui/visitor/b.vue
+++ b/packages/client/src/ui/visitor/b.vue
@@ -86,10 +86,9 @@ import XKanban from "./kanban.vue";
 import { host, instanceName } from "@/config";
 import { search } from "@/scripts/search";
 import * as os from "@/os";
-import { instance } from "@/instance";
 import XSigninDialog from "@/components/MkSigninDialog.vue";
 import XSignupDialog from "@/components/MkSignupDialog.vue";
-import { ColdDeviceStorage, defaultStore } from "@/store";
+import { defaultStore } from "@/store";
 import { mainRouter } from "@/router";
 import type { PageMetadata } from "@/scripts/page-metadata";
 import { provideMetadataReceiver } from "@/scripts/page-metadata";
@@ -108,29 +107,11 @@ provideMetadataReceiver((info) => {
 	}
 });
 
-const announcements = {
-	endpoint: "announcements",
-	limit: 10,
-};
-const isTimelineAvailable =
-	!instance.disableLocalTimeline ||
-	!instance.disableRecommendedTimeline ||
-	!instance.disableGlobalTimeline;
 const showMenu = ref(false);
 const isDesktop = ref(window.innerWidth >= DESKTOP_THRESHOLD);
 const narrow = ref(window.innerWidth < 1280);
 const meta = ref();
 
-const keymap = computed(() => {
-	return {
-		d: () => {
-			if (ColdDeviceStorage.get("syncDeviceDarkMode")) return;
-			defaultStore.set("darkMode", !defaultStore.state.darkMode);
-		},
-		s: search,
-	};
-});
-
 const root = computed(() => mainRouter.currentRoute.value.name === "index");
 
 os.api("meta", { detail: true }).then((res) => {
@@ -227,9 +208,6 @@ defineExpose({
 		flex: 1;
 		min-width: 0;
 
-		> .banner {
-		}
-
 		> .contents {
 			position: relative;
 			z-index: 1;
diff --git a/packages/client/src/ui/visitor/kanban.vue b/packages/client/src/ui/visitor/kanban.vue
index ccccbc6dd..dc88e9667 100644
--- a/packages/client/src/ui/visitor/kanban.vue
+++ b/packages/client/src/ui/visitor/kanban.vue
@@ -26,7 +26,11 @@
 					<div v-if="meta" class="about">
 						<div
 							class="desc"
-							v-html="meta.description || i18n.ts.introFirefish"
+							v-html="
+								meta.description !== ''
+									? meta.description
+									: i18n.ts.introFirefish
+							"
 						></div>
 					</div>
 					<div class="action">
diff --git a/packages/client/src/widgets/federation.vue b/packages/client/src/widgets/federation.vue
index 3224a7207..708d81acf 100644
--- a/packages/client/src/widgets/federation.vue
+++ b/packages/client/src/widgets/federation.vue
@@ -33,7 +33,7 @@
 							>{{ instance.host }}</a
 						>
 						<p>
-							{{ instance.softwareName || "?" }}
+							{{ instance.softwareName ?? "?" }}
 							{{ instance.softwareVersion }}
 						</p>
 					</div>
diff --git a/packages/client/src/widgets/server-info.vue b/packages/client/src/widgets/server-info.vue
index 5ee6f31cd..48a2e4be5 100644
--- a/packages/client/src/widgets/server-info.vue
+++ b/packages/client/src/widgets/server-info.vue
@@ -9,8 +9,8 @@
 			<div :class="$style.iconContainer">
 				<img
 					:src="
-						$instance.iconUrl ||
-						$instance.faviconUrl ||
+						$instance.faviconUrl ??
+						$instance.iconUrl ??
 						'/favicon.ico'
 					"
 					alt="Instance logo"