diff --git a/packages/backend/package.json b/packages/backend/package.json
index c6c76b30a..2ff70e0ed 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -111,7 +111,6 @@
 		"tsconfig-paths": "4.0.0",
 		"twemoji-parser": "14.0.0",
 		"typeorm": "0.3.6",
-		"ulid": "2.3.0",
 		"unzipper": "0.10.11",
 		"uuid": "8.3.2",
 		"web-push": "3.5.0",
diff --git a/packages/backend/src/misc/gen-id.ts b/packages/backend/src/misc/gen-id.ts
index fcf476857..1a7a511b6 100644
--- a/packages/backend/src/misc/gen-id.ts
+++ b/packages/backend/src/misc/gen-id.ts
@@ -1,21 +1,23 @@
-import { ulid } from 'ulid';
-import { genAid } from './id/aid.js';
-import { genMeid } from './id/meid.js';
-import { genMeidg } from './id/meidg.js';
-import { genObjectId } from './id/object-id.js';
-import config from '@/config/index.js';
+import * as crypto from 'node:crypto';
 
-const metohd = config.id.toLowerCase();
+// AID generation
+// 8 chars: milliseconds elapsed since 2000-01-01 00:00:00.000Z encoded as base36
+// + 2 random chars
+
+const TIME2000 = 946684800000;
+let counter = crypto.randomBytes(2).readUInt16LE(0);
 
 export function genId(date?: Date): string {
 	if (!date || (date > new Date())) date = new Date();
 
-	switch (metohd) {
-		case 'aid': return genAid(date);
-		case 'meid': return genMeid(date);
-		case 'meidg': return genMeidg(date);
-		case 'ulid': return ulid(date.getTime());
-		case 'objectid': return genObjectId(date);
-		default: throw new Error('unrecognized id generation method');
-	}
+	let t = date.getTime();
+	t -= TIME2000;
+	if (t < 0) t = 0;
+	if (isNaN(t)) throw 'Failed to create AID: Invalid Date';
+	const time = t.toString(36).padStart(8, '0');
+
+	counter++;
+	const noise = counter.toString(36).padStart(2, '0').slice(-2);
+
+	return time + noise;
 }
diff --git a/packages/backend/src/misc/id/aid.ts b/packages/backend/src/misc/id/aid.ts
deleted file mode 100644
index 87e688826..000000000
--- a/packages/backend/src/misc/id/aid.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-// AID
-// 長さ8の[2000年1月1日からの経過ミリ秒をbase36でエンコードしたもの] + 長さ2の[ノイズ文字列]
-
-import * as crypto from 'node:crypto';
-
-const TIME2000 = 946684800000;
-let counter = crypto.randomBytes(2).readUInt16LE(0);
-
-function getTime(time: number) {
-	time = time - TIME2000;
-	if (time < 0) time = 0;
-
-	return time.toString(36).padStart(8, '0');
-}
-
-function getNoise() {
-	return counter.toString(36).padStart(2, '0').slice(-2);
-}
-
-export function genAid(date: Date): string {
-	const t = date.getTime();
-	if (isNaN(t)) throw 'Failed to create AID: Invalid Date';
-	counter++;
-	return getTime(t) + getNoise();
-}
diff --git a/packages/backend/src/misc/id/meid.ts b/packages/backend/src/misc/id/meid.ts
deleted file mode 100644
index 30bbdf169..000000000
--- a/packages/backend/src/misc/id/meid.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-const CHARS = '0123456789abcdef';
-
-function getTime(time: number) {
-	if (time < 0) time = 0;
-	if (time === 0) {
-		return CHARS[0];
-	}
-
-	time += 0x800000000000;
-
-	return time.toString(16).padStart(12, CHARS[0]);
-}
-
-function getRandom() {
-	let str = '';
-
-	for (let i = 0; i < 12; i++) {
-		str += CHARS[Math.floor(Math.random() * CHARS.length)];
-	}
-
-	return str;
-}
-
-export function genMeid(date: Date): string {
-	return getTime(date.getTime()) + getRandom();
-}
diff --git a/packages/backend/src/misc/id/meidg.ts b/packages/backend/src/misc/id/meidg.ts
deleted file mode 100644
index d4aaaea1b..000000000
--- a/packages/backend/src/misc/id/meidg.ts
+++ /dev/null
@@ -1,28 +0,0 @@
-const CHARS = '0123456789abcdef';
-
-//  4bit Fixed hex value 'g'
-// 44bit UNIX Time ms in Hex
-// 48bit Random value in Hex
-
-function getTime(time: number) {
-	if (time < 0) time = 0;
-	if (time === 0) {
-		return CHARS[0];
-	}
-
-	return time.toString(16).padStart(11, CHARS[0]);
-}
-
-function getRandom() {
-	let str = '';
-
-	for (let i = 0; i < 12; i++) {
-		str += CHARS[Math.floor(Math.random() * CHARS.length)];
-	}
-
-	return str;
-}
-
-export function genMeidg(date: Date): string {
-	return 'g' + getTime(date.getTime()) + getRandom();
-}
diff --git a/packages/backend/src/misc/id/object-id.ts b/packages/backend/src/misc/id/object-id.ts
deleted file mode 100644
index 392ea4330..000000000
--- a/packages/backend/src/misc/id/object-id.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-const CHARS = '0123456789abcdef';
-
-function getTime(time: number) {
-	if (time < 0) time = 0;
-	if (time === 0) {
-		return CHARS[0];
-	}
-
-	time = Math.floor(time / 1000);
-
-	return time.toString(16).padStart(8, CHARS[0]);
-}
-
-function getRandom() {
-	let str = '';
-
-	for (let i = 0; i < 16; i++) {
-		str += CHARS[Math.floor(Math.random() * CHARS.length)];
-	}
-
-	return str;
-}
-
-export function genObjectId(date: Date): string {
-	return getTime(date.getTime()) + getRandom();
-}