diff --git a/packages/backend/src/core/CreateSystemUserService.ts b/packages/backend/src/core/CreateSystemUserService.ts
index 14d814b0e6..71c2db77ab 100644
--- a/packages/backend/src/core/CreateSystemUserService.ts
+++ b/packages/backend/src/core/CreateSystemUserService.ts
@@ -5,8 +5,7 @@
 
 import { randomUUID } from 'node:crypto';
 import { Inject, Injectable } from '@nestjs/common';
-import * as argon2 from 'argon2';
-//import bcrypt from 'bcryptjs';
+import bcrypt from 'bcryptjs';
 import { IsNull, DataSource } from 'typeorm';
 import { genRsaKeyPair } from '@/misc/gen-key-pair.js';
 import { MiUser } from '@/models/User.js';
@@ -33,8 +32,8 @@ export class CreateSystemUserService {
 		const password = randomUUID();
 
 		// Generate hash of password
-		//const salt = await bcrypt.genSalt(8);
-		const hash = await argon2.hash(password);
+		const salt = await bcrypt.genSalt(8);
+		const hash = await bcrypt.hash(password, salt);
 
 		// Generate secret
 		const secret = generateNativeUserToken();
diff --git a/packages/backend/src/core/SignupService.ts b/packages/backend/src/core/SignupService.ts
index 80907a8921..8020a266d6 100644
--- a/packages/backend/src/core/SignupService.ts
+++ b/packages/backend/src/core/SignupService.ts
@@ -5,8 +5,7 @@
 
 import { generateKeyPair } from 'node:crypto';
 import { Inject, Injectable } from '@nestjs/common';
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { DataSource, IsNull } from 'typeorm';
 import { DI } from '@/di-symbols.js';
 import type { UsedUsernamesRepository, UsersRepository } from '@/models/_.js';
@@ -71,8 +70,8 @@ export class SignupService {
 			}
 
 			// Generate hash of password
-			//const salt = await bcrypt.genSalt(8);
-			hash = await argon2.hash(password);
+			const salt = await bcrypt.genSalt(8);
+			hash = await bcrypt.hash(password, salt);
 		}
 
 		// Generate secret
diff --git a/packages/backend/src/server/api/SigninApiService.ts b/packages/backend/src/server/api/SigninApiService.ts
index 6fbcacbc11..0fcaabc082 100644
--- a/packages/backend/src/server/api/SigninApiService.ts
+++ b/packages/backend/src/server/api/SigninApiService.ts
@@ -139,7 +139,22 @@ export class SigninApiService {
 		}
 
 		// Compare password
-		const same = await argon2.verify(profile.password!, password) || bcrypt.compareSync(password, profile.password!);
+		let same;
+
+		if (profile.password?.startsWith('$argon2')) {
+			same = await argon2.verify(profile.password, password);
+
+			if (same) {
+				// rehash
+				const salt = await bcrypt.genSalt(8);
+				const newHash = await bcrypt.hash(password, salt);
+				await this.userProfilesRepository.update(user.id, {
+					password: newHash,
+				});
+			}
+		} else {
+			same = await bcrypt.compare(password, profile.password!);
+		}
 
 		const fail = async (status?: number, failure?: { id: string }) => {
 			// Append signin history
@@ -156,12 +171,6 @@ export class SigninApiService {
 
 		if (!profile.twoFactorEnabled) {
 			if (same) {
-				if (profile.password!.startsWith('$2')) {
-					const newHash = await argon2.hash(password);
-					this.userProfilesRepository.update(user.id, {
-						password: newHash
-					});
-				}
 				if (!instance.approvalRequiredForSignup && !user.approved) this.usersRepository.update(user.id, { approved: true });
 
 				return this.signinService.signin(request, reply, user);
@@ -180,12 +189,6 @@ export class SigninApiService {
 			}
 
 			try {
-				if (profile.password!.startsWith('$2')) {
-					const newHash = await argon2.hash(password);
-					this.userProfilesRepository.update(user.id, {
-						password: newHash
-					});
-				}
 				await this.userAuthService.twoFactorAuthenticate(profile, token);
 			} catch (e) {
 				return await fail(403, {
diff --git a/packages/backend/src/server/api/SignupApiService.ts b/packages/backend/src/server/api/SignupApiService.ts
index f89c3954f8..d9dfa23a03 100644
--- a/packages/backend/src/server/api/SignupApiService.ts
+++ b/packages/backend/src/server/api/SignupApiService.ts
@@ -4,8 +4,7 @@
  */
 
 import { Inject, Injectable } from '@nestjs/common';
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { IsNull } from 'typeorm';
 import { DI } from '@/di-symbols.js';
 import type { RegistrationTicketsRepository, UsedUsernamesRepository, UserPendingsRepository, UserProfilesRepository, UsersRepository, MiRegistrationTicket } from '@/models/_.js';
@@ -20,10 +19,10 @@ import { MiLocalUser } from '@/models/User.js';
 import { FastifyReplyError } from '@/misc/fastify-reply-error.js';
 import { bindThis } from '@/decorators.js';
 import { L_CHARS, secureRndstr } from '@/misc/secure-rndstr.js';
-import { SigninService } from './SigninService.js';
-import type { FastifyRequest, FastifyReply } from 'fastify';
-import instance from './endpoints/charts/instance.js';
 import { RoleService } from '@/core/RoleService.js';
+import { SigninService } from './SigninService.js';
+import instance from './endpoints/charts/instance.js';
+import type { FastifyRequest, FastifyReply } from 'fastify';
 
 @Injectable()
 export class SignupApiService {
@@ -193,8 +192,8 @@ export class SignupApiService {
 			const code = secureRndstr(16, { chars: L_CHARS });
 
 			// Generate hash of password
-			//const salt = await bcrypt.genSalt(8);
-			const hash = await argon2.hash(password);
+			const salt = await bcrypt.genSalt(8);
+			const hash = await bcrypt.hash(password, salt);
 
 			const pendingUser = await this.userPendingsRepository.insertOne({
 				id: this.idService.gen(),
diff --git a/packages/backend/src/server/api/endpoints/admin/reset-password.ts b/packages/backend/src/server/api/endpoints/admin/reset-password.ts
index 828dbae712..6450da48a3 100644
--- a/packages/backend/src/server/api/endpoints/admin/reset-password.ts
+++ b/packages/backend/src/server/api/endpoints/admin/reset-password.ts
@@ -4,8 +4,7 @@
  */
 
 import { Inject, Injectable } from '@nestjs/common';
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UsersRepository, UserProfilesRepository } from '@/models/_.js';
 import { DI } from '@/di-symbols.js';
@@ -66,7 +65,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			const passwd = secureRndstr(8);
 
 			// Generate hash of password
-			const hash = await argon2.hash(passwd);
+			const salt = await bcrypt.genSalt(8);
+			const hash = await bcrypt.hash(passwd, salt);
 
 			await this.userProfilesRepository.update({
 				userId: user.id,
diff --git a/packages/backend/src/server/api/endpoints/i/2fa/key-done.ts b/packages/backend/src/server/api/endpoints/i/2fa/key-done.ts
index 084d4af658..8c988e429a 100644
--- a/packages/backend/src/server/api/endpoints/i/2fa/key-done.ts
+++ b/packages/backend/src/server/api/endpoints/i/2fa/key-done.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
@@ -94,7 +93,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password ?? '', ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password ?? '');
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/2fa/register-key.ts b/packages/backend/src/server/api/endpoints/i/2fa/register-key.ts
index 6ab50a57c9..9a42631a16 100644
--- a/packages/backend/src/server/api/endpoints/i/2fa/register-key.ts
+++ b/packages/backend/src/server/api/endpoints/i/2fa/register-key.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UserProfilesRepository } from '@/models/_.js';
@@ -226,7 +225,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password ?? '', ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password ?? '');
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/2fa/register.ts b/packages/backend/src/server/api/endpoints/i/2fa/register.ts
index 888d0fc6ef..dead15cee4 100644
--- a/packages/backend/src/server/api/endpoints/i/2fa/register.ts
+++ b/packages/backend/src/server/api/endpoints/i/2fa/register.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import * as OTPAuth from 'otpauth';
 import * as QRCode from 'qrcode';
 import { Inject, Injectable } from '@nestjs/common';
@@ -85,7 +84,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password ?? '', ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password ?? '');
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/2fa/remove-key.ts b/packages/backend/src/server/api/endpoints/i/2fa/remove-key.ts
index 614fd0c498..1454ddebf1 100644
--- a/packages/backend/src/server/api/endpoints/i/2fa/remove-key.ts
+++ b/packages/backend/src/server/api/endpoints/i/2fa/remove-key.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UserProfilesRepository, UserSecurityKeysRepository } from '@/models/_.js';
@@ -75,7 +74,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password ?? '', ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password ?? '');
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/2fa/unregister.ts b/packages/backend/src/server/api/endpoints/i/2fa/unregister.ts
index 2773825373..f7373ed6fd 100644
--- a/packages/backend/src/server/api/endpoints/i/2fa/unregister.ts
+++ b/packages/backend/src/server/api/endpoints/i/2fa/unregister.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
@@ -70,7 +69,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password ?? '', ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password ?? '');
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/change-password.ts b/packages/backend/src/server/api/endpoints/i/change-password.ts
index f131c7e9d1..1a392eaa63 100644
--- a/packages/backend/src/server/api/endpoints/i/change-password.ts
+++ b/packages/backend/src/server/api/endpoints/i/change-password.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UserProfilesRepository } from '@/models/_.js';
@@ -58,15 +57,15 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password!, ps.currentPassword);
+			const passwordMatched = await bcrypt.compare(ps.currentPassword, profile.password!);
 
 			if (!passwordMatched) {
 				throw new Error('incorrect password');
 			}
 
 			// Generate hash of password
-			//const salt = await bcrypt.genSalt(8);
-			const hash = await argon2.hash(ps.newPassword);
+			const salt = await bcrypt.genSalt(8);
+			const hash = await bcrypt.hash(ps.newPassword, salt);
 
 			await this.userProfilesRepository.update(me.id, {
 				password: hash,
diff --git a/packages/backend/src/server/api/endpoints/i/delete-account.ts b/packages/backend/src/server/api/endpoints/i/delete-account.ts
index 565eaaafc0..a98894d488 100644
--- a/packages/backend/src/server/api/endpoints/i/delete-account.ts
+++ b/packages/backend/src/server/api/endpoints/i/delete-account.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import type { UsersRepository, UserProfilesRepository } from '@/models/_.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
@@ -67,7 +66,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				return;
 			}
 
-			const passwordMatched = await argon2.verify(profile.password!, ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password!);
 			if (!passwordMatched) {
 				throw new Error('incorrect password');
 			}
diff --git a/packages/backend/src/server/api/endpoints/i/regenerate-token.ts b/packages/backend/src/server/api/endpoints/i/regenerate-token.ts
index 814ffb5488..60fd073377 100644
--- a/packages/backend/src/server/api/endpoints/i/regenerate-token.ts
+++ b/packages/backend/src/server/api/endpoints/i/regenerate-token.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UsersRepository, UserProfilesRepository } from '@/models/_.js';
@@ -51,7 +50,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			const profile = await this.userProfilesRepository.findOneByOrFail({ userId: me.id });
 
 			// Compare password
-			const same = await argon2.verify(profile.password!, ps.password);
+			const same = await bcrypt.compare(ps.password, profile.password!);
 
 			if (!same) {
 				throw new Error('incorrect password');
diff --git a/packages/backend/src/server/api/endpoints/i/update-email.ts b/packages/backend/src/server/api/endpoints/i/update-email.ts
index 7332026d84..eea657ebbd 100644
--- a/packages/backend/src/server/api/endpoints/i/update-email.ts
+++ b/packages/backend/src/server/api/endpoints/i/update-email.ts
@@ -5,8 +5,7 @@
 
 import { Inject, Injectable } from '@nestjs/common';
 import ms from 'ms';
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { UserProfilesRepository } from '@/models/_.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
@@ -96,7 +95,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			const passwordMatched = await argon2.verify(profile.password!, ps.password);
+			const passwordMatched = await bcrypt.compare(ps.password, profile.password!);
 			if (!passwordMatched) {
 				throw new ApiError(meta.errors.incorrectPassword);
 			}
diff --git a/packages/backend/src/server/api/endpoints/reset-password.ts b/packages/backend/src/server/api/endpoints/reset-password.ts
index 1639b57bc5..9693892637 100644
--- a/packages/backend/src/server/api/endpoints/reset-password.ts
+++ b/packages/backend/src/server/api/endpoints/reset-password.ts
@@ -3,8 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-//import bcrypt from 'bcryptjs';
-import * as argon2 from 'argon2';
+import bcrypt from 'bcryptjs';
 import { Inject, Injectable } from '@nestjs/common';
 import type { UserProfilesRepository, PasswordResetRequestsRepository } from '@/models/_.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
@@ -54,8 +53,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			}
 
 			// Generate hash of password
-			//const salt = await bcrypt.genSalt(8);
-			const hash = await argon2.hash(ps.password);
+			const salt = await bcrypt.genSalt(8);
+			const hash = await bcrypt.hash(ps.password, salt);
 
 			await this.userProfilesRepository.update(req.userId, {
 				password: hash,