diff --git a/backend/nest-cli.json b/backend/nest-cli.json
index f9aa683..3e472d0 100644
--- a/backend/nest-cli.json
+++ b/backend/nest-cli.json
@@ -3,6 +3,13 @@
   "collection": "@nestjs/schematics",
   "sourceRoot": "src",
   "compilerOptions": {
-    "deleteOutDir": true
+    "deleteOutDir": true,
+    "assets": [
+      {
+        "include": "module/i18n/locales/**/*",
+        "outDir": "dist"
+      }
+    ],
+    "watchAssets": true
   }
 }
diff --git a/backend/package-lock.json b/backend/package-lock.json
index 125fda8..d4b51ad 100644
--- a/backend/package-lock.json
+++ b/backend/package-lock.json
@@ -35,6 +35,7 @@
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         "joi": "^17.13.3",
         "nest-winston": "^1.10.2",
+        "nestjs-i18n": "^10.8.4",
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         "passport": "^0.7.0",
         "passport-github2": "^0.1.12",
@@ -2038,6 +2039,50 @@
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       }
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+      "resolved": "https://registry.npmjs.org/@messageformat/core/-/core-3.4.0.tgz",
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+      "license": "MIT",
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+        "@messageformat/number-skeleton": "^1.0.0",
+        "@messageformat/parser": "^5.1.0",
+        "@messageformat/runtime": "^3.0.1",
+        "make-plural": "^7.0.0",
+        "safe-identifier": "^0.4.1"
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+    },
+    "node_modules/@messageformat/date-skeleton": {
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+      "resolved": "https://registry.npmjs.org/@messageformat/date-skeleton/-/date-skeleton-1.1.0.tgz",
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+      "license": "MIT"
+    },
+    "node_modules/@messageformat/number-skeleton": {
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+      "resolved": "https://registry.npmjs.org/@messageformat/number-skeleton/-/number-skeleton-1.2.0.tgz",
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+      "license": "MIT"
+    },
+    "node_modules/@messageformat/parser": {
+      "version": "5.1.1",
+      "resolved": "https://registry.npmjs.org/@messageformat/parser/-/parser-5.1.1.tgz",
+      "integrity": "sha512-3p0YRGCcTUCYvBKLIxtDDyrJ0YijGIwrTRu1DT8gIviIDZru8H23+FkY6MJBzM1n9n20CiM4VeDYuBsrrwnLjg==",
+      "license": "MIT",
+      "dependencies": {
+        "moo": "^0.5.1"
+      }
+    },
+    "node_modules/@messageformat/runtime": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/@messageformat/runtime/-/runtime-3.0.2.tgz",
+      "integrity": "sha512-dkIPDCjXcfhSHgNE1/qV6TeczQZR59Yx0xXeafVKgK3QVWoxc38ljwpksUpnzCGvN151KUbCJTDZVmahtf1YZw==",
+      "license": "MIT",
+      "dependencies": {
+        "make-plural": "^7.0.0"
+      }
+    },
     "node_modules/@microsoft/tsdoc": {
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       "resolved": "https://registry.npmjs.org/@microsoft/tsdoc/-/tsdoc-0.16.0.tgz",
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@@ -4697,6 +4728,18 @@
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+      "resolved": "https://registry.npmjs.org/binary-extensions/-/binary-extensions-2.3.0.tgz",
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+      "license": "MIT",
+      "engines": {
+        "node": ">=8"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
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@@ -4841,7 +4883,6 @@
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-      "license": "MIT",
-      "peer": true
+      "license": "MIT"
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@@ -7840,6 +7875,18 @@
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@@ -9453,6 +9496,12 @@
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       "license": "ISC"
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+      "version": "7.5.0",
+      "resolved": "https://registry.npmjs.org/make-plural/-/make-plural-7.5.0.tgz",
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@@ -9644,6 +9693,12 @@
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+      "resolved": "https://registry.npmjs.org/moo/-/moo-0.5.3.tgz",
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@@ -9789,6 +9845,109 @@
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+      "version": "10.8.4",
+      "resolved": "https://registry.npmjs.org/nestjs-i18n/-/nestjs-i18n-10.8.4.tgz",
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+      "dependencies": {
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+        "chokidar": "^3.6.0",
+        "cookie": "^1.1.1",
+        "string-format": "^2.0.0",
+        "yaml": "^2.8.3"
+      },
+      "bin": {
+        "nestjs-i18n": "bin/nestjs-i18n.mjs"
+      },
+      "engines": {
+        "node": ">=22"
+      },
+      "peerDependencies": {
+        "@nestjs/common": "*",
+        "@nestjs/core": "*",
+        "class-validator": "*",
+        "rxjs": "*"
+      },
+      "peerDependenciesMeta": {
+        "class-validator": {
+          "optional": true
+        }
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+      "resolved": "https://registry.npmjs.org/chokidar/-/chokidar-3.6.0.tgz",
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+        "braces": "~3.0.2",
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+        "readdirp": "~3.6.0"
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+      "engines": {
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+      "funding": {
+        "url": "https://paulmillr.com/funding/"
+      },
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+      }
+    },
+    "node_modules/nestjs-i18n/node_modules/cookie": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-1.1.1.tgz",
+      "integrity": "sha512-ei8Aos7ja0weRpFzJnEA9UHJ/7XQmqglbRwnf2ATjcB9Wq874VKH9kfjjirM6UhU2/E5fFYadylyhFldcqSidQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/express"
+      }
+    },
+    "node_modules/nestjs-i18n/node_modules/glob-parent": {
+      "version": "5.1.2",
+      "resolved": "https://registry.npmjs.org/glob-parent/-/glob-parent-5.1.2.tgz",
+      "integrity": "sha512-AOIgSQCepiJYwP3ARnGx+5VnTu2HBYdzbGP45eLw1vr3zB3vZLeyed1sC9hnbcOc9/SrMyM5RPQrkGz4aS9Zow==",
+      "license": "ISC",
+      "dependencies": {
+        "is-glob": "^4.0.1"
+      },
+      "engines": {
+        "node": ">= 6"
+      }
+    },
+    "node_modules/nestjs-i18n/node_modules/picomatch": {
+      "version": "2.3.2",
+      "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-2.3.2.tgz",
+      "integrity": "sha512-V7+vQEJ06Z+c5tSye8S+nHUfI51xoXIXjHQ99cQtKUkQqqO1kO/KCJUfZXuB47h/YBlDhah2H3hdUGXn8ie0oA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=8.6"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/jonschlinkert"
+      }
+    },
+    "node_modules/nestjs-i18n/node_modules/readdirp": {
+      "version": "3.6.0",
+      "resolved": "https://registry.npmjs.org/readdirp/-/readdirp-3.6.0.tgz",
+      "integrity": "sha512-hOS089on8RduqdbhvQ5Z37A0ESjsqz6qnRcffsMU3495FuTdqSm+7bhJ29JvIOsBDEEnan5DPu9t3To9VRlMzA==",
+      "license": "MIT",
+      "dependencies": {
+        "picomatch": "^2.2.1"
+      },
+      "engines": {
+        "node": ">=8.10.0"
+      }
+    },
     "node_modules/node-abort-controller": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/node-abort-controller/-/node-abort-controller-3.1.1.tgz",
@@ -10109,7 +10268,6 @@
       "resolved": "https://registry.npmjs.org/passport/-/passport-0.7.0.tgz",
       "integrity": "sha512-cPLl+qZpSc+ireUvt+IzqbED1cHHkDoVYMo30jbJIdOOjQ1MQYZBPiNvmi8UM6lJuOpTPXJGZQk0DtC4y61MYQ==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "passport-strategy": "1.x.x",
         "pause": "0.0.1",
@@ -10307,7 +10465,6 @@
       "resolved": "https://registry.npmjs.org/pg/-/pg-8.20.0.tgz",
       "integrity": "sha512-ldhMxz2r8fl/6QkXnBD3CR9/xg694oT6DZQ2s6c/RI28OjtSOpxnPrUCGOBJ46RCUxcWdx3p6kw/xnDHjKvaRA==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "pg-connection-string": "^2.12.0",
         "pg-pool": "^3.13.0",
@@ -10573,7 +10730,6 @@
       "integrity": "sha512-7igPTM53cGHMW8xWuVTydi2KO233VFiTNyF5hLJqpilHfmn8C8gPf+PS7dUT64YcXFbiMGZxS9pCSxL/Dxm/Jw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "bin": {
         "prettier": "bin/prettier.cjs"
       },
@@ -10839,7 +10995,6 @@
       "resolved": "https://registry.npmjs.org/redis/-/redis-5.12.1.tgz",
       "integrity": "sha512-LDsoVvb/CpoV9EN3FXvgvSHNJWuCIzl9MiO3ppOevuGLpSGJhwfQjpEwfFJcQvNSddHADDdZaWx0HnmMxRXG7g==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@redis/bloom": "5.12.1",
         "@redis/client": "5.12.1",
@@ -11152,6 +11307,12 @@
       ],
       "license": "MIT"
     },
+    "node_modules/safe-identifier": {
+      "version": "0.4.2",
+      "resolved": "https://registry.npmjs.org/safe-identifier/-/safe-identifier-0.4.2.tgz",
+      "integrity": "sha512-6pNbSMW6OhAi9j+N8V+U715yBQsaWJ7eyEUaOrawX+isg5ZxhUlV1NipNtgaKHmFGiABwt+ZF04Ii+3Xjkg+8w==",
+      "license": "ISC"
+    },
     "node_modules/safe-stable-stringify": {
       "version": "2.5.0",
       "resolved": "https://registry.npmjs.org/safe-stable-stringify/-/safe-stable-stringify-2.5.0.tgz",
@@ -11204,7 +11365,6 @@
       "integrity": "sha512-fgFx7Hfoq60ytK2c7DhnF8jIvzYgOMxfugjLOSMHjLIPgenqa7S7oaagATUq99mV6IYvN2tRmC0wnTYX6iPbMw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "fast-deep-equal": "^3.1.1",
         "fast-json-stable-stringify": "^2.0.0",
@@ -11714,6 +11874,12 @@
         "safe-buffer": "~5.2.0"
       }
     },
+    "node_modules/string-format": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/string-format/-/string-format-2.0.0.tgz",
+      "integrity": "sha512-bbEs3scLeYNXLecRRuk6uJxdXUSj6le/8rNPHChIJTn2V79aXVTR1EH2OH5zLKKoz0V02fOUKZZcw01pLUShZA==",
+      "license": "WTFPL OR MIT"
+    },
     "node_modules/string-length": {
       "version": "4.0.2",
       "resolved": "https://registry.npmjs.org/string-length/-/string-length-4.0.2.tgz",
@@ -12224,7 +12390,6 @@
       "version": "5.0.1",
       "resolved": "https://registry.npmjs.org/to-regex-range/-/to-regex-range-5.0.1.tgz",
       "integrity": "sha512-65P7iz6X5yEr1cwcgvQxbbIw7Uk3gOy5dIdtZ4rDveLqhrdJP+Li/Hx6tyK0NEb+2GCyneCMJiGqrADCSNk8sQ==",
-      "dev": true,
       "license": "MIT",
       "dependencies": {
         "is-number": "^7.0.0"
@@ -12390,7 +12555,6 @@
       "integrity": "sha512-f0FFpIdcHgn8zcPSbf1dRevwt047YMnaiJM3u2w2RewrB+fob/zePZcrOyQoLMMO7aBIddLcQIEK5dYjkLnGrQ==",
       "devOptional": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@cspotcode/source-map-support": "^0.8.0",
         "@tsconfig/node10": "^1.0.7",
@@ -12556,7 +12720,6 @@
       "resolved": "https://registry.npmjs.org/typeorm/-/typeorm-0.3.28.tgz",
       "integrity": "sha512-6GH7wXhtfq2D33ZuRXYwIsl/qM5685WZcODZb7noOOcRMteM9KF2x2ap3H0EBjnSV0VO4gNAfJT5Ukp0PkOlvg==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@sqltools/formatter": "^1.2.5",
         "ansis": "^4.2.0",
@@ -12782,7 +12945,6 @@
       "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
       "devOptional": true,
       "license": "Apache-2.0",
-      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -13161,6 +13323,7 @@
       "integrity": "sha512-Wx0Kx52hxE7C18hkMEggYlEifqWZtYaRgouJor+WMdPnQyEK13vgEWyVNup7SoeeoLMsr4kf5h6dOW11I15MUA==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "ajv": "^8.0.0"
       },
@@ -13179,6 +13342,7 @@
       "integrity": "sha512-2NxwbF/hZ0KpepYN0cNbo+FN6XoK7GaHlQhgx/hIZl6Va0bF45RQOOwhLIy8lQDbuCiadSLCBnH2CFYquit5bw==",
       "dev": true,
       "license": "BSD-2-Clause",
+      "peer": true,
       "dependencies": {
         "esrecurse": "^4.3.0",
         "estraverse": "^4.1.1"
@@ -13193,6 +13357,7 @@
       "integrity": "sha512-39nnKffWz8xN1BU/2c79n9nB9HDzo0niYUqx6xyqUnyoAnQyyWpOTdZEeiCch8BBu515t4wp9ZmgVfVhn9EBpw==",
       "dev": true,
       "license": "BSD-2-Clause",
+      "peer": true,
       "engines": {
         "node": ">=4.0"
       }
@@ -13203,6 +13368,7 @@
       "integrity": "sha512-eflK8wEtyOE6+hsaRVPxvUKYCpRgzLqDTb8krvAsRIwOGlHoSgYLgBXoubGgLd2fT41/OUYdb48v4k4WWHQurA==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@types/json-schema": "^7.0.9",
         "ajv": "^8.9.0",
@@ -13270,7 +13436,6 @@
       "resolved": "https://registry.npmjs.org/winston/-/winston-3.19.0.tgz",
       "integrity": "sha512-LZNJgPzfKR+/J3cHkxcpHKpKKvGfDZVPS4hfJCc4cCG0CgYzvlD6yE/S3CIL/Yt91ak327YCpiF/0MyeZHEHKA==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@colors/colors": "^1.6.0",
         "@dabh/diagnostics": "^2.0.8",
@@ -13440,6 +13605,21 @@
       "dev": true,
       "license": "ISC"
     },
+    "node_modules/yaml": {
+      "version": "2.9.0",
+      "resolved": "https://registry.npmjs.org/yaml/-/yaml-2.9.0.tgz",
+      "integrity": "sha512-2AvhNX3mb8zd6Zy7INTtSpl1F15HW6Wnqj0srWlkKLcpYl/gMIMJiyuGq2KeI2YFxUPjdlB+3Lc10seMLtL4cA==",
+      "license": "ISC",
+      "bin": {
+        "yaml": "bin.mjs"
+      },
+      "engines": {
+        "node": ">= 14.6"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/eemeli"
+      }
+    },
     "node_modules/yargs": {
       "version": "17.7.2",
       "resolved": "https://registry.npmjs.org/yargs/-/yargs-17.7.2.tgz",
diff --git a/backend/package.json b/backend/package.json
index e5bdd22..ce35cde 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -46,6 +46,7 @@
     "ioredis": "^5.10.1",
     "joi": "^17.13.3",
     "nest-winston": "^1.10.2",
+    "nestjs-i18n": "^10.8.4",
     "nodemailer": "^7.0.12",
     "passport": "^0.7.0",
     "passport-github2": "^0.1.12",
diff --git a/backend/src/app.module.ts b/backend/src/app.module.ts
index 9b380b8..ed15326 100644
--- a/backend/src/app.module.ts
+++ b/backend/src/app.module.ts
@@ -7,9 +7,12 @@ import { AppController } from './app.controller';
 import { AppService } from './app.service';
 import { AuthModule } from './auth/auth.module';
 import { buildWinstonOptions } from './common/logger.config';
+import { HttpExceptionFilter } from './common/filters/http-exception.filter';
 import { LoggerMiddleware } from './common/middleware/logger.middleware';
 import { DocumentsModule } from './documents/documents.module';
 import { MailModule } from './mail/mail.module';
+import { I18nModule } from './module/i18n/i18n.module';
+import { UserProfileModule } from './module/user-profile/user-profile.module';
 import { UserActivityModule } from './module/user-activity/user-activity.module';
 import { QueueModule } from './queue/queue.module';
 import { RiskAssessmentModule } from './risk-assessment/risk-assessment.module';
@@ -53,6 +56,8 @@ import { ConfigValidationSchema } from './config/config.validation';
     UsersModule,
     AuthModule,
     DocumentsModule,
+    I18nModule,
+    UserProfileModule,
     PublicVerificationModule,
     UserActivityModule,
     RiskAssessmentModule,
@@ -62,7 +67,7 @@ import { ConfigValidationSchema } from './config/config.validation';
     QueueModule,
   ],
   controllers: [AppController],
-  providers: [AppService, LoggerMiddleware],
+  providers: [AppService, LoggerMiddleware, HttpExceptionFilter],
 })
 export class AppModule implements NestModule {
   configure(consumer: MiddlewareConsumer) {
diff --git a/backend/src/common/filters/http-exception.filter.ts b/backend/src/common/filters/http-exception.filter.ts
index b1c67c4..a8b6ccb 100644
--- a/backend/src/common/filters/http-exception.filter.ts
+++ b/backend/src/common/filters/http-exception.filter.ts
@@ -1,4 +1,4 @@
-import {
+import {
   ArgumentsHost,
   Catch,
   ExceptionFilter,
@@ -6,13 +6,19 @@
   HttpStatus,
   Logger,
 } from '@nestjs/common';
-import { Response, Request } from 'express';
+import { ConfigService } from '@nestjs/config';
+import { Request, Response } from 'express';
+
+import { MultiLanguageSupportService } from '../../module/i18n/multi-language-support.service';
 
 @Catch()
 export class HttpExceptionFilter implements ExceptionFilter {
   private readonly logger = new Logger(HttpExceptionFilter.name);
 
-  constructor(private readonly isProduction = false) {}
+  constructor(
+    private readonly languageService: MultiLanguageSupportService,
+    private readonly configService: ConfigService,
+  ) {}
 
   catch(exception: unknown, host: ArgumentsHost) {
     const ctx = host.switchToHttp();
@@ -26,9 +32,15 @@ export class HttpExceptionFilter implements ExceptionFilter {
 
     const errorResponse = isHttp
       ? exception.getResponse()
-      : { message: (exception as Error)?.message }; // fallback message
+      : { message: (exception as Error)?.message };
 
-    const { message, error } = this.normalizeResponse(errorResponse, exception);
+    const languageCode = this.resolveLanguage(request);
+    const { message, error } = this.normalizeResponse(
+      errorResponse,
+      exception,
+      status,
+      languageCode,
+    );
 
     const payload = {
       statusCode: status,
@@ -38,12 +50,12 @@ export class HttpExceptionFilter implements ExceptionFilter {
       path: request.url,
     };
 
-    this.logger.error(
-      `${status}   -> `,
-      (exception as Error)?.stack,
-    );
+    this.logger.error(`${status}   -> `, (exception as Error)?.stack);
 
-    if (!this.isProduction && exception instanceof Error) {
+    if (
+      this.configService.get<string>('NODE_ENV') !== 'production' &&
+      exception instanceof Error
+    ) {
       Object.assign(payload, { stack: exception.stack });
     }
 
@@ -53,29 +65,77 @@ export class HttpExceptionFilter implements ExceptionFilter {
   private normalizeResponse(
     response: string | object | null | undefined,
     exception: unknown,
+    status: HttpStatus,
+    languageCode: string,
   ) {
-    let message = 'Internal server error';
+    let message = this.translateStatus(status, languageCode);
     let error = HttpStatus.INTERNAL_SERVER_ERROR.toString();
 
     if (typeof response === 'string') {
-      message = response;
+      message = message || response;
     } else if (response && typeof response === 'object') {
       const body = response as Record<string, any>;
-      if (body.message) {
-        message = Array.isArray(body.message)
-          ? body.message.join(', ')
-          : body.message;
-      } else if (exception instanceof Error && exception.message) {
-        message = exception.message;
+      if (!message) {
+        if (body.message) {
+          message = Array.isArray(body.message)
+            ? body.message.join(', ')
+            : body.message;
+        } else if (exception instanceof Error && exception.message) {
+          message = exception.message;
+        }
       }
 
       if (body.error) {
         error = body.error;
       }
-    } else if (exception instanceof Error) {
+    } else if (exception instanceof Error && !message) {
       message = exception.message;
     }
 
     return { message, error };
   }
+
+  private resolveLanguage(request: Request) {
+    const user = (
+      request as Request & {
+        user?: { preferredLanguage?: string };
+      }
+    ).user;
+    const preferredLanguage = user?.preferredLanguage;
+
+    if (
+      preferredLanguage &&
+      this.languageService.isSupported(preferredLanguage)
+    ) {
+      return preferredLanguage;
+    }
+
+    return 'en';
+  }
+
+  private translateStatus(status: HttpStatus, languageCode: string) {
+    if (status === HttpStatus.BAD_REQUEST) {
+      return this.languageService.translate(
+        'errors.validationFailed',
+        languageCode,
+      );
+    }
+
+    if (status === HttpStatus.FORBIDDEN) {
+      return this.languageService.translate('errors.forbidden', languageCode);
+    }
+
+    if (status === HttpStatus.NOT_FOUND) {
+      return this.languageService.translate('errors.notFound', languageCode);
+    }
+
+    if (status === HttpStatus.INTERNAL_SERVER_ERROR) {
+      return this.languageService.translate(
+        'errors.internalServerError',
+        languageCode,
+      );
+    }
+
+    return '';
+  }
 }
diff --git a/backend/src/main.ts b/backend/src/main.ts
index 25997b9..2244fd7 100644
--- a/backend/src/main.ts
+++ b/backend/src/main.ts
@@ -38,11 +38,7 @@ async function bootstrap() {
     }),
   );
 
-  app.useGlobalFilters(
-    new HttpExceptionFilter(
-      configService.get<string>('NODE_ENV') === 'production',
-    ),
-  );
+  app.useGlobalFilters(app.get(HttpExceptionFilter));
 
   // Swagger documentation
   const config = new DocumentBuilder()
diff --git a/backend/src/module/i18n/i18n.module.ts b/backend/src/module/i18n/i18n.module.ts
new file mode 100644
index 0000000..a25b50e
--- /dev/null
+++ b/backend/src/module/i18n/i18n.module.ts
@@ -0,0 +1,24 @@
+import { Module } from '@nestjs/common';
+import { I18nModule as NestI18nModule } from 'nestjs-i18n';
+import { AcceptLanguageResolver, I18nJsonLoader } from 'nestjs-i18n';
+import { join } from 'path';
+
+import { MultiLanguageSupportService } from './multi-language-support.service';
+
+@Module({
+  imports: [
+    NestI18nModule.forRoot({
+      fallbackLanguage: 'en',
+      loader: I18nJsonLoader,
+      loaderOptions: {
+        path: join(__dirname, 'locales'),
+        watch: true,
+      },
+      resolvers: [new AcceptLanguageResolver({ matchType: 'strict-loose' })],
+      logging: false,
+    }),
+  ],
+  providers: [MultiLanguageSupportService],
+  exports: [MultiLanguageSupportService],
+})
+export class I18nModule {}
diff --git a/backend/src/module/i18n/locales/en/en.json b/backend/src/module/i18n/locales/en/en.json
new file mode 100644
index 0000000..693e3af
--- /dev/null
+++ b/backend/src/module/i18n/locales/en/en.json
@@ -0,0 +1,12 @@
+{
+  "errors": {
+    "validationFailed": "Validation failed",
+    "forbidden": "Forbidden",
+    "notFound": "Not found",
+    "internalServerError": "Internal server error",
+    "unsupportedLanguage": "Unsupported language code"
+  },
+  "language": {
+    "updated": "Language preference updated"
+  }
+}
diff --git a/backend/src/module/i18n/locales/fr/fr.json b/backend/src/module/i18n/locales/fr/fr.json
new file mode 100644
index 0000000..96deb13
--- /dev/null
+++ b/backend/src/module/i18n/locales/fr/fr.json
@@ -0,0 +1,12 @@
+{
+  "errors": {
+    "validationFailed": "La validation a échoué",
+    "forbidden": "Interdit",
+    "notFound": "Introuvable",
+    "internalServerError": "Erreur interne du serveur",
+    "unsupportedLanguage": "Code de langue non pris en charge"
+  },
+  "language": {
+    "updated": "Préférence de langue mise à jour"
+  }
+}
diff --git a/backend/src/module/i18n/multi-language-support.service.ts b/backend/src/module/i18n/multi-language-support.service.ts
new file mode 100644
index 0000000..82feaf5
--- /dev/null
+++ b/backend/src/module/i18n/multi-language-support.service.ts
@@ -0,0 +1,96 @@
+import { Injectable, OnModuleInit } from '@nestjs/common';
+import { I18nService } from 'nestjs-i18n';
+import { readFile, readdir } from 'fs/promises';
+import { join } from 'path';
+
+type LocaleData = Record<string, unknown>;
+
+@Injectable()
+export class MultiLanguageSupportService implements OnModuleInit {
+  private readonly localesPath = join(__dirname, 'locales');
+  private supportedLanguages: string[] = ['en'];
+
+  constructor(private readonly i18nService: I18nService) {}
+
+  async onModuleInit() {
+    await this.validateLocaleFiles();
+  }
+
+  translate(key: string, lang: string) {
+    return this.i18nService.translate(key, { lang });
+  }
+
+  isSupported(languageCode: string) {
+    return this.supportedLanguages.includes(languageCode);
+  }
+
+  getSupportedLanguages() {
+    return [...this.supportedLanguages];
+  }
+
+  private async validateLocaleFiles() {
+    const entries = await readdir(this.localesPath, { withFileTypes: true });
+    const localeDirs = entries.filter((entry) => entry.isDirectory());
+
+    this.supportedLanguages = localeDirs.map((entry) => entry.name);
+
+    if (!this.supportedLanguages.includes('en')) {
+      throw new Error('English locale is required');
+    }
+
+    const english = await this.loadLocale('en');
+
+    for (const languageCode of this.supportedLanguages) {
+      const locale = await this.loadLocale(languageCode);
+      const missingKeys = this.findMissingKeys(english, locale);
+      if (missingKeys.length > 0) {
+        throw new Error(
+          `Locale ${languageCode} is missing keys: ${missingKeys.join(', ')}`,
+        );
+      }
+    }
+  }
+
+  private async loadLocale(languageCode: string): Promise<LocaleData> {
+    const filePath = join(
+      this.localesPath,
+      languageCode,
+      `${languageCode}.json`,
+    );
+    const raw = await readFile(filePath, 'utf8');
+
+    try {
+      return JSON.parse(raw) as LocaleData;
+    } catch {
+      throw new Error(`Invalid JSON in locale file ${filePath}`);
+    }
+  }
+
+  private findMissingKeys(
+    source: LocaleData,
+    target: LocaleData,
+    prefix = '',
+  ): string[] {
+    const missing: string[] = [];
+
+    for (const [key, value] of Object.entries(source)) {
+      const currentKey = prefix ? `${prefix}.${key}` : key;
+      const targetValue = target[key];
+
+      if (targetValue === undefined) {
+        missing.push(currentKey);
+        continue;
+      }
+
+      if (this.isPlainObject(value) && this.isPlainObject(targetValue)) {
+        missing.push(...this.findMissingKeys(value, targetValue, currentKey));
+      }
+    }
+
+    return missing;
+  }
+
+  private isPlainObject(value: unknown): value is LocaleData {
+    return !!value && typeof value === 'object' && !Array.isArray(value);
+  }
+}
diff --git a/backend/src/module/user-profile/dto/update-language.dto.ts b/backend/src/module/user-profile/dto/update-language.dto.ts
new file mode 100644
index 0000000..e2a2585
--- /dev/null
+++ b/backend/src/module/user-profile/dto/update-language.dto.ts
@@ -0,0 +1,6 @@
+import { IsIn } from 'class-validator';
+
+export class UpdateLanguageDto {
+  @IsIn(['en', 'fr'])
+  languageCode: string;
+}
diff --git a/backend/src/module/user-profile/user-profile.controller.ts b/backend/src/module/user-profile/user-profile.controller.ts
index 4f81da1..ec19dfa 100644
--- a/backend/src/module/user-profile/user-profile.controller.ts
+++ b/backend/src/module/user-profile/user-profile.controller.ts
@@ -3,6 +3,7 @@ import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { JwtAuthGuard } from '../../auth/guards/jwt-auth.guard';
 import { User } from '../../users/entities/user.entity';
+import { UpdateLanguageDto } from './dto/update-language.dto';
 
 @Controller('module/users')
 @UseGuards(JwtAuthGuard)
@@ -14,8 +15,11 @@ export class UserProfileController {
 
   @Get('me')
   getProfile(@Req() req: { user: User }) {
-    const { passwordHash, twoFactorSecret, twoFactorBackupCodes, ...profile } = req.user;
-    void passwordHash; void twoFactorSecret; void twoFactorBackupCodes;
+    const { passwordHash, twoFactorSecret, twoFactorBackupCodes, ...profile } =
+      req.user;
+    void passwordHash;
+    void twoFactorSecret;
+    void twoFactorBackupCodes;
     return profile;
   }
 
@@ -26,8 +30,29 @@ export class UserProfileController {
   ) {
     await this.users.update(req.user.id, body);
     const updated = await this.users.findOneByOrFail({ id: req.user.id });
-    const { passwordHash, twoFactorSecret, twoFactorBackupCodes, ...profile } = updated;
-    void passwordHash; void twoFactorSecret; void twoFactorBackupCodes;
+    const { passwordHash, twoFactorSecret, twoFactorBackupCodes, ...profile } =
+      updated;
+    void passwordHash;
+    void twoFactorSecret;
+    void twoFactorBackupCodes;
     return profile;
   }
-}
\ No newline at end of file
+
+  @Patch('me/language')
+  async updateLanguage(
+    @Req() req: { user: User },
+    @Body() body: UpdateLanguageDto,
+  ) {
+    await this.users.update(req.user.id, {
+      preferredLanguage: body.languageCode,
+    });
+
+    const updated = await this.users.findOneByOrFail({ id: req.user.id });
+    const { passwordHash, twoFactorSecret, twoFactorBackupCodes, ...profile } =
+      updated;
+    void passwordHash;
+    void twoFactorSecret;
+    void twoFactorBackupCodes;
+    return profile;
+  }
+}
diff --git a/backend/src/module/user-profile/user-profile.module.ts b/backend/src/module/user-profile/user-profile.module.ts
new file mode 100644
index 0000000..263fd32
--- /dev/null
+++ b/backend/src/module/user-profile/user-profile.module.ts
@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+
+import { UserProfileController } from './user-profile.controller';
+import { User } from '../../users/entities/user.entity';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([User])],
+  controllers: [UserProfileController],
+})
+export class UserProfileModule {}