diff --git a/packages/backend/src/const.ts b/packages/backend/src/const.ts
index c56fed19c..82a093100 100644
--- a/packages/backend/src/const.ts
+++ b/packages/backend/src/const.ts
@@ -1,31 +1,32 @@
 import config from "@/config/index.js";
 
 export const MAX_NOTE_TEXT_LENGTH =
-	config.maxNoteLength != null ? config.maxNoteLength : 3000;
+	config.maxNoteLength != null ? config.maxNoteLength : 3000; // <- should we increase this?
 
 export const SECOND = 1000;
-export const SEC = 1000;
+export const SEC = 1000; // why do we need this duplicate here?
 export const MINUTE = 60 * SEC;
-export const MIN = 60 * SEC;
+export const MIN = 60 * SEC; // why do we need this duplicate here?
 export const HOUR = 60 * MIN;
 export const DAY = 24 * HOUR;
 
-export const USER_ONLINE_THRESHOLD = 1000 * 60 * 10; // 10min
-export const USER_ACTIVE_THRESHOLD = 1000 * 60 * 60 * 24 * 3; // 3days
+export const USER_ONLINE_THRESHOLD = 10 * MINUTE;
+export const USER_ACTIVE_THRESHOLD = 3 * DAY;
 
-// ブラウザで直接表示することを許可するファイルの種類のリスト
-// ここに含まれないものは application/octet-stream としてレスポンスされる
-// SVGはXSSを生むので許可しない
+// List of file types allowed to be viewed directly in the browser
+// Anything not included here will be responded as application/octet-stream
+// SVG is not allowed because it generates XSS <- we need to fix this and later allow it to be viewed directly
 export const FILE_TYPE_BROWSERSAFE = [
 	// Images
 	"image/png",
-	"image/gif",
+	"image/gif", // TODO: deprecated, but still used by old notes, new gifs should be converted to webp in the future
 	"image/jpeg",
-	"image/webp",
+	"image/webp", // TODO: make this the default image format
 	"image/apng",
 	"image/bmp",
 	"image/tiff",
 	"image/x-icon",
+	"image/avif", // not as good supported now, but its good to introduce initial support for the future
 
 	// OggS
 	"audio/opus",
@@ -35,12 +36,17 @@ export const FILE_TYPE_BROWSERSAFE = [
 
 	// ISO/IEC base media file format
 	"video/quicktime",
-	"video/mp4",
+	"video/mp4", // TODO: we need to check for av1 later
+	"video/vnd.avi", // also av1
 	"audio/mp4",
 	"video/x-m4v",
 	"audio/x-m4a",
 	"video/3gpp",
 	"video/3gpp2",
+	"video/3gp2",
+	"audio/3gpp",
+	"audio/3gpp2",
+	"audio/3gp2",
 
 	"video/mpeg",
 	"audio/mpeg",
@@ -50,6 +56,7 @@ export const FILE_TYPE_BROWSERSAFE = [
 
 	"audio/aac",
 	"audio/x-flac",
+	"audio/flac",
 	"audio/vnd.wave",
 ];
 /*