diff --git a/locales/index.d.ts b/locales/index.d.ts
index 09af138430..1d756a14d8 100644
--- a/locales/index.d.ts
+++ b/locales/index.d.ts
@@ -1834,6 +1834,8 @@ export interface Locale {
         "checkBackupCodesBeforeCloseThisWizard": string;
         "backupCodes": string;
         "backupCodesDescription": string;
+        "backupCodeUsedWarning": string;
+        "backupCodesExhaustedWarning": string;
     };
     "_permissions": {
         "read:account": string;
diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index c20d2aac80..3396a3a832 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -1752,6 +1752,8 @@ _2fa:
   checkBackupCodesBeforeCloseThisWizard: "このウィザードを閉じる前に、以下のバックアップコードを確認してください。"
   backupCodes: "バックアップコード"
   backupCodesDescription: "認証アプリが使用できなくなった場合、以下のバックアップコードを使ってアカウントにアクセスできます。これらのコードは必ず安全な場所に保管してください。各コードは一回だけ使用できます。"
+  backupCodeUsedWarning: "バックアップコードが使用されました。認証アプリが使えなくなっている場合、なるべく早く認証アプリを再設定してください。"
+  backupCodesExhaustedWarning: "バックアップコードが全て使用されました。認証アプリを利用できない場合、これ以上アカウントにアクセスできなくなります。認証アプリを再登録してください。"
 
 _permissions:
   "read:account": "アカウントの情報を見る"
diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index 236ee9f0b4..d12fd1b620 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -434,6 +434,7 @@ export class UserEntityService implements OnModuleInit {
 				preventAiLearning: profile!.preventAiLearning,
 				isExplorable: user.isExplorable,
 				isDeleted: user.isDeleted,
+				twoFactorBackupCodesStock: profile?.twoFactorBackupSecret?.length === 5 ? 'full' : (profile?.twoFactorBackupSecret?.length ?? 0) > 0 ? 'partial' : 'none',
 				hideOnlineStatus: user.hideOnlineStatus,
 				hasUnreadSpecifiedNotes: this.noteUnreadsRepository.count({
 					where: { userId: user.id, isSpecified: true },
diff --git a/packages/backend/src/models/json-schema/user.ts b/packages/backend/src/models/json-schema/user.ts
index 0c205654eb..3314464c31 100644
--- a/packages/backend/src/models/json-schema/user.ts
+++ b/packages/backend/src/models/json-schema/user.ts
@@ -321,6 +321,11 @@ export const packedMeDetailedOnlySchema = {
 			type: 'boolean',
 			nullable: false, optional: false,
 		},
+		twoFactorBackupCodesStock: {
+			type: 'string',
+			enum: ['full', 'partial', 'none'],
+			nullable: false, optional: false,
+		},
 		hideOnlineStatus: {
 			type: 'boolean',
 			nullable: false, optional: false,
diff --git a/packages/backend/test/e2e/users.ts b/packages/backend/test/e2e/users.ts
index 8afbcbe322..2c396813ff 100644
--- a/packages/backend/test/e2e/users.ts
+++ b/packages/backend/test/e2e/users.ts
@@ -152,6 +152,7 @@ describe('ユーザー', () => {
 			preventAiLearning: user.preventAiLearning,
 			isExplorable: user.isExplorable,
 			isDeleted: user.isDeleted,
+			twoFactorBackupCodesStock: user.twoFactorBackupCodesStock,
 			hideOnlineStatus: user.hideOnlineStatus,
 			hasUnreadSpecifiedNotes: user.hasUnreadSpecifiedNotes,
 			hasUnreadMentions: user.hasUnreadMentions,
@@ -398,6 +399,7 @@ describe('ユーザー', () => {
 		assert.strictEqual(response.preventAiLearning, true);
 		assert.strictEqual(response.isExplorable, true);
 		assert.strictEqual(response.isDeleted, false);
+		assert.strictEqual(response.twoFactorBackupCodesStock, 'none');
 		assert.strictEqual(response.hideOnlineStatus, false);
 		assert.strictEqual(response.hasUnreadSpecifiedNotes, false);
 		assert.strictEqual(response.hasUnreadMentions, false);
diff --git a/packages/frontend/.storybook/changes.ts b/packages/frontend/.storybook/changes.ts
index a1275132be..0cc648fbae 100644
--- a/packages/frontend/.storybook/changes.ts
+++ b/packages/frontend/.storybook/changes.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import fs from 'node:fs/promises';
 import { fileURLToPath } from 'node:url';
 import path from 'node:path';
diff --git a/packages/frontend/.storybook/fakes.ts b/packages/frontend/.storybook/fakes.ts
index a4289cff7d..14481deeea 100644
--- a/packages/frontend/.storybook/fakes.ts
+++ b/packages/frontend/.storybook/fakes.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import type { entities } from 'misskey-js'
 
 export function abuseUserReport() {
@@ -110,6 +115,7 @@ export function userDetailed(id = 'someuserid', username = 'miskist', host = 'mi
 		publicReactions: false,
 		securityKeys: false,
 		twoFactorEnabled: false,
+		twoFactorBackupCodesStock: 'none',
 		updatedAt: null,
 		uri: null,
 		url: null,
diff --git a/packages/frontend/.storybook/generate.tsx b/packages/frontend/.storybook/generate.tsx
index d47d8672c7..d61df9e7be 100644
--- a/packages/frontend/.storybook/generate.tsx
+++ b/packages/frontend/.storybook/generate.tsx
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { existsSync, readFileSync } from 'node:fs';
 import { writeFile } from 'node:fs/promises';
 import { basename, dirname } from 'node:path/posix';
diff --git a/packages/frontend/.storybook/main.ts b/packages/frontend/.storybook/main.ts
index b64979980a..a450f8b46b 100644
--- a/packages/frontend/.storybook/main.ts
+++ b/packages/frontend/.storybook/main.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import type { StorybookConfig } from '@storybook/vue3-vite';
diff --git a/packages/frontend/.storybook/manager.ts b/packages/frontend/.storybook/manager.ts
index 5653deee84..8f501111d0 100644
--- a/packages/frontend/.storybook/manager.ts
+++ b/packages/frontend/.storybook/manager.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { addons } from '@storybook/manager-api';
 import { create } from '@storybook/theming/create';
 
diff --git a/packages/frontend/.storybook/mocks.ts b/packages/frontend/.storybook/mocks.ts
index 4091e39686..b60755feea 100644
--- a/packages/frontend/.storybook/mocks.ts
+++ b/packages/frontend/.storybook/mocks.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { type SharedOptions, rest } from 'msw';
 
 export const onUnhandledRequest = ((req, print) => {
diff --git a/packages/frontend/.storybook/preload-locale.ts b/packages/frontend/.storybook/preload-locale.ts
index 2b7362b88d..349cc13508 100644
--- a/packages/frontend/.storybook/preload-locale.ts
+++ b/packages/frontend/.storybook/preload-locale.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { writeFile } from 'node:fs/promises';
 import locales from '../../../locales/index.js';
 
diff --git a/packages/frontend/.storybook/preload-theme.ts b/packages/frontend/.storybook/preload-theme.ts
index 42fbeff738..ad2cf18a35 100644
--- a/packages/frontend/.storybook/preload-theme.ts
+++ b/packages/frontend/.storybook/preload-theme.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { readFile, writeFile } from 'node:fs/promises';
 import JSON5 from 'json5';
 
diff --git a/packages/frontend/.storybook/preview.ts b/packages/frontend/.storybook/preview.ts
index 67c81c666b..9860b60c67 100644
--- a/packages/frontend/.storybook/preview.ts
+++ b/packages/frontend/.storybook/preview.ts
@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 import { addons } from '@storybook/addons';
 import { FORCE_REMOUNT } from '@storybook/core-events';
 import { type Preview, setup } from '@storybook/vue3';
diff --git a/packages/frontend/src/pages/settings/2fa.vue b/packages/frontend/src/pages/settings/2fa.vue
index 8b29fc9e82..6871091aad 100644
--- a/packages/frontend/src/pages/settings/2fa.vue
+++ b/packages/frontend/src/pages/settings/2fa.vue
@@ -8,6 +8,13 @@ SPDX-License-Identifier: AGPL-3.0-only
 	<template #label>{{ i18n.ts['2fa'] }}</template>
 
 	<div v-if="$i" class="_gaps_s">
+		<MkInfo v-if="$i.twoFactorEnabled && $i.twoFactorBackupCodesStock === 'partial'" warn>
+			{{ i18n.ts._2fa.backupCodeUsedWarning }}
+		</MkInfo>
+		<MkInfo v-if="$i.twoFactorEnabled && $i.twoFactorBackupCodesStock === 'none'" warn>
+			{{ i18n.ts._2fa.backupCodesExhaustedWarning }}
+		</MkInfo>
+
 		<MkFolder :defaultOpen="true">
 			<template #icon><i class="ti ti-shield-lock"></i></template>
 			<template #label>{{ i18n.ts.totp }}</template>
diff --git a/packages/misskey-js/etc/misskey-js.api.md b/packages/misskey-js/etc/misskey-js.api.md
index aa9c2157b6..4d17d69152 100644
--- a/packages/misskey-js/etc/misskey-js.api.md
+++ b/packages/misskey-js/etc/misskey-js.api.md
@@ -2462,6 +2462,7 @@ type MeDetailed = UserDetailed & {
     receiveAnnouncementEmail: boolean;
     usePasswordLessLogin: boolean;
     unreadAnnouncements: Announcement[];
+    twoFactorBackupCodesStock: 'full' | 'partial' | 'none';
     [other: string]: any;
 };
 
diff --git a/packages/misskey-js/src/entities.ts b/packages/misskey-js/src/entities.ts
index f0c6104ed3..64742fa5b6 100644
--- a/packages/misskey-js/src/entities.ts
+++ b/packages/misskey-js/src/entities.ts
@@ -105,6 +105,7 @@ export type MeDetailed = UserDetailed & {
 	receiveAnnouncementEmail: boolean;
 	usePasswordLessLogin: boolean;
 	unreadAnnouncements: Announcement[];
+	twoFactorBackupCodesStock: 'full' | 'partial' | 'none';
 	[other: string]: any;
 };