diff --git a/packages/backend/src/core/IdService.ts b/packages/backend/src/core/IdService.ts
index 94084ad84f..8aa6ccfc4e 100644
--- a/packages/backend/src/core/IdService.ts
+++ b/packages/backend/src/core/IdService.ts
@@ -3,10 +3,11 @@ import { ulid } from 'ulid';
 import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
 import { genAid, parseAid } from '@/misc/id/aid.js';
-import { genMeid } from '@/misc/id/meid.js';
-import { genMeidg } from '@/misc/id/meidg.js';
+import { genMeid, parseMeid } from '@/misc/id/meid.js';
+import { genMeidg, parseMeidg } from '@/misc/id/meidg.js';
 import { genObjectId } from '@/misc/id/object-id.js';
 import { bindThis } from '@/decorators.js';
+import { parseUlid } from '@/misc/id/ulid.js';
 
 @Injectable()
 export class IdService {
@@ -37,11 +38,10 @@ export class IdService {
 	public parse(id: string): { date: Date; } {
 		switch (this.method) {
 			case 'aid': return parseAid(id);
-			// TODO
-			//case 'meid':
-			//case 'meidg':
-			//case 'ulid':
-			//case 'objectid':
+			case 'objectid':
+			case 'meid': return parseMeid(id);
+			case 'meidg': return parseMeidg(id);
+			case 'ulid': return parseUlid(id);
 			default: throw new Error('unrecognized id generation method');
 		}
 	}
diff --git a/packages/backend/src/misc/id/aid.ts b/packages/backend/src/misc/id/aid.ts
index 93a9929aa7..9e206ee98f 100644
--- a/packages/backend/src/misc/id/aid.ts
+++ b/packages/backend/src/misc/id/aid.ts
@@ -3,6 +3,8 @@
 
 import * as crypto from 'node:crypto';
 
+export const aidRegExp = /^[0-9a-z]{10}$/;
+
 const TIME2000 = 946684800000;
 let counter = crypto.randomBytes(2).readUInt16LE(0);
 
diff --git a/packages/backend/src/misc/id/meid.ts b/packages/backend/src/misc/id/meid.ts
index 30bbdf1698..337416b059 100644
--- a/packages/backend/src/misc/id/meid.ts
+++ b/packages/backend/src/misc/id/meid.ts
@@ -1,5 +1,8 @@
 const CHARS = '0123456789abcdef';
 
+// same as object-id
+export const meidRegExp = /^[0-9a-f]{24}$/;
+
 function getTime(time: number) {
 	if (time < 0) time = 0;
 	if (time === 0) {
@@ -24,3 +27,9 @@ function getRandom() {
 export function genMeid(date: Date): string {
 	return getTime(date.getTime()) + getRandom();
 }
+
+export function parseMeid(id: string): { date: Date; } {
+	return {
+		date: new Date(parseInt(id.slice(0, 12), 16) - 0x800000000000),
+	};
+}
diff --git a/packages/backend/src/misc/id/meidg.ts b/packages/backend/src/misc/id/meidg.ts
index d4aaaea1ba..19d0bc1fd2 100644
--- a/packages/backend/src/misc/id/meidg.ts
+++ b/packages/backend/src/misc/id/meidg.ts
@@ -3,6 +3,7 @@ const CHARS = '0123456789abcdef';
 //  4bit Fixed hex value 'g'
 // 44bit UNIX Time ms in Hex
 // 48bit Random value in Hex
+export const meidgRegExp = /^g[0-9a-f]{23}$/;
 
 function getTime(time: number) {
 	if (time < 0) time = 0;
@@ -26,3 +27,9 @@ function getRandom() {
 export function genMeidg(date: Date): string {
 	return 'g' + getTime(date.getTime()) + getRandom();
 }
+
+export function parseMeidg(id: string): { date: Date; } {
+	return {
+		date: new Date(parseInt(id.slice(1, 12), 16)),
+	};
+}
diff --git a/packages/backend/src/misc/id/object-id.ts b/packages/backend/src/misc/id/object-id.ts
index 392ea43301..aec3447bd7 100644
--- a/packages/backend/src/misc/id/object-id.ts
+++ b/packages/backend/src/misc/id/object-id.ts
@@ -1,5 +1,8 @@
 const CHARS = '0123456789abcdef';
 
+// same as meid
+export const objectIdRegExp = /^[0-9a-f]{24}$/;
+
 function getTime(time: number) {
 	if (time < 0) time = 0;
 	if (time === 0) {
@@ -24,3 +27,9 @@ function getRandom() {
 export function genObjectId(date: Date): string {
 	return getTime(date.getTime()) + getRandom();
 }
+
+export function parseObjectId(id: string): { date: Date; } {
+	return {
+		date: new Date(parseInt(id.slice(0, 8), 16) * 1000),
+	};
+}
diff --git a/packages/backend/src/misc/id/ulid.ts b/packages/backend/src/misc/id/ulid.ts
new file mode 100644
index 0000000000..e8aa752890
--- /dev/null
+++ b/packages/backend/src/misc/id/ulid.ts
@@ -0,0 +1,14 @@
+// Crockford's Base32
+// https://github.com/ulid/spec#encoding
+const CHARS = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
+
+export const ulidRegExp = /^[0123456789ABCDEFGHJKMNPQRSTVWXYZ]{26}$/;
+
+export function parseUlid(id: string): { date: Date; } {
+    const timestamp = id.slice(0, 10);
+    let time = 0;
+    for (let i = 0; i < 10; i++) {
+        time = time * 32 + CHARS.indexOf(timestamp[i]);
+    }
+    return { date: new Date(time) };
+}
diff --git a/packages/backend/test/unit/misc/id.ts b/packages/backend/test/unit/misc/id.ts
new file mode 100644
index 0000000000..ecd0e60a31
--- /dev/null
+++ b/packages/backend/test/unit/misc/id.ts
@@ -0,0 +1,44 @@
+import { aidRegExp, genAid, parseAid } from '@/misc/id/aid.js';
+import { genMeid, meidRegExp, parseMeid } from '@/misc/id/meid.js';
+import { genMeidg, meidgRegExp, parseMeidg } from '@/misc/id/meidg.js';
+import { genObjectId, objectIdRegExp, parseObjectId } from '@/misc/id/object-id.js';
+import { ulidRegExp, parseUlid } from '@/misc/id/ulid.js';
+import { ulid } from 'ulid';
+import { describe, test, expect } from '@jest/globals';
+
+describe('misc:id', () => {
+    test('aid', () => {
+        const date = new Date();
+        const gotAid = genAid(date);
+        expect(gotAid).toMatch(aidRegExp);
+        expect(parseAid(gotAid).date.getTime()).toBe(date.getTime());
+    });
+
+    test('meid', () => {
+        const date = new Date();
+        const gotMeid = genMeid(date);
+        expect(gotMeid).toMatch(meidRegExp);
+        expect(parseMeid(gotMeid).date.getTime()).toBe(date.getTime());
+    });
+
+    test('meidg', () => {
+        const date = new Date();
+        const gotMeidg = genMeidg(date);
+        expect(gotMeidg).toMatch(meidgRegExp);
+        expect(parseMeidg(gotMeidg).date.getTime()).toBe(date.getTime());
+    });
+
+    test('objectid', () => {
+        const date = new Date();
+        const gotObjectId = genObjectId(date);
+        expect(gotObjectId).toMatch(objectIdRegExp);
+        expect(Math.floor(parseObjectId(gotObjectId).date.getTime() / 1000)).toBe(Math.floor(date.getTime() / 1000));
+    });
+
+    test('ulid', () => {
+        const date = new Date();
+        const gotUlid = ulid(date.getTime());
+        expect(gotUlid).toMatch(ulidRegExp);
+        expect(parseUlid(gotUlid).date.getTime()).toBe(date.getTime());
+    });
+});