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expressjs skill

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This skill helps you understand Express.js APIs and best practices across versions, routing, middleware, and error handling for robust Node applications.

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SKILL.md

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---
name: "expressjs"
description: "Scraped from https://expressjs.com/ Source: https://expressjs.com. Use when questions involve: 2024, 2025, de, en, es, fr."
---

# Expressjs

> Official documentation: https://expressjs.com

## Overview

This skill provides comprehensive documentation for expressjs.

**Total references:** 141 files (~1,248,723 tokens)

**Topics covered:**
Moderate severity vulnerability CVE-2024-43796 in Express core, 모델을 어떻게 정의해야 합니까, Autres considérations, Performance, Middleware integrato, Cómo configuro un manejador de errores, Exemplos adicionais, 性能表现, Prototype, 如何处理 404 响应, 移行の例, 路由路径...

## Reference Files

Load only the reference files relevant to the user's question:

### 2024

- **[Welcome to The Express Blog! and more](references/2024.md)** (~4,850 tokens)
  - Topics: High severity vulnerability CVE-2024-45590 in body-parser middleware, High severity vulnerability CVE-2024-47178 in basic-auth-connect middleware, Moderate severity vulnerability CVE-2024-43796 in Express core

### 2025

- **[A New Chapter for Express.js: Triumphs of 2024 and an ambitious 2025 and more](references/2025.md)** (~6,670 tokens)
  - Topics: A Transformative 2024, A Bold Vision for 2025, The Road Ahead

### De

- **[3.x](references/de-1.md)** (~2,841 tokens)
  - Topics: Application
- **[4.x](references/de-2.md)** (~21,057 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/de-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[Best Practices in Produktionsumgebungen: Leistung und Zuverlässigkeit and more](references/de-4.md)** (~7,870 tokens)
  - Topics: Things to do in your code, Things to do in your environment  setup, Überblick
- **[5.x API](references/de-5.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[Express hinter Proxys and more](references/de-6.md)** (~7,360 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Wechsel zu Express 5 and more](references/de-7.md)** (~7,991 tokens)
  - Topics: Überblick, Express 5 Codemods, Änderungen in Express 5
- **[Template and more](references/de-8.md)** (~6,706 tokens)
  - Topics: Überblick, Technical committee, Express is made of many modules
- **[body and more](references/de-9.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/de-10.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/de-11.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/de-12.md)** (~7,871 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/de-13.md)** (~2,908 tokens)
  - Topics: Additional examples, Wie muss ich meine Anwendung strukturieren, Wie definiere ich Modelle

### En

- **[3.x API](references/en-1.md)** (~7,060 tokens)
  - Topics: express, Application, Request
- **[4.x API](references/en-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/en-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[Production best practices: performance and reliability and more](references/en-4.md)** (~7,732 tokens)
  - Topics: Things to do in your code, Things to do in your environment  setup, Overview
- **[5.x API](references/en-5.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[Express Blog Posts and more](references/en-6.md)** (~6,007 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Moving to Express 4 and more](references/en-7.md)** (~6,672 tokens)
  - Topics: Overview, Changes in Express 4, Example app migration
- **[Routing and more](references/en-8.md)** (~6,411 tokens)
  - Topics: Route methods, Route paths, Route parameters
- **[Contributing to Express and more](references/en-9.md)** (~5,775 tokens)
  - Topics: Technical committee, Community contributing guide, Collaborators guide
- **[body and more](references/en-10.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/en-11.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/en-12.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/en-13.md)** (~7,841 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/en-14.md)** (~2,922 tokens)
  - Topics: Additional examples, How should I structure my application, How do I define models

### Es

- **[API de 3.x](references/es-1.md)** (~2,848 tokens)
  - Topics: Application
- **[API de 4.x](references/es-2.md)** (~21,062 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/es-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[Production best practices: performance and reliability and more](references/es-4.md)** (~7,530 tokens)
  - Topics: Cosas que hacer en el código, Cosas que hacer en el entorno  configuración, Overview
- **[Actualizaciones de seguridad](references/es-5.md)** (~1,053 tokens)
- **[5.x API](references/es-6.md)** (~20,043 tokens)
  - Topics: express, Application, Request
- **[Express detrás de proxies and more](references/es-7.md)** (~7,368 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Migración a Express 5 and more](references/es-8.md)** (~6,606 tokens)
  - Topics: Overview, Express 5 Codemods, Changes in Express 5
- **[Utilización del middleware and more](references/es-9.md)** (~3,192 tokens)
  - Topics: Application-level middleware, Middleware de nivel de direccionador, Error-handling middleware
- **[Contribuir a Express and more](references/es-10.md)** (~5,526 tokens)
  - Topics: Technical committee, Community contributing guide, Collaborators guide
- **[body and more](references/es-11.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/es-12.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/es-13.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/es-14.md)** (~7,944 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/es-15.md)** (~3,030 tokens)
  - Topics: Additional examples, How should I structure my application, Cómo debo definir los modelos

### Fr

- **[API 3.x](references/fr-1.md)** (~2,845 tokens)
  - Topics: Application
- **[API 4.x](references/fr-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/fr-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[Meilleures pratiques en production : performances et fiabilité and more](references/fr-4.md)** (~7,599 tokens)
  - Topics: A faire dans votre code, A faire dans votre environnementconfiguration, Présentation
- **[Mises à jour de sécurité](references/fr-5.md)** (~1,012 tokens)
- **[5.x API](references/fr-6.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[Serveurs proxy derrière Express and more](references/fr-7.md)** (~7,832 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Migration vers Express 5 and more](references/fr-8.md)** (~6,663 tokens)
  - Topics: Présentation, Express 5 Codemods, Modifications dans Express 5
- **[Utilisation de middleware and more](references/fr-9.md)** (~3,122 tokens)
  - Topics: Middleware niveau application, Middleware niveau routeur, Middleware de traitement derreurs
- **[Contributing to Express and more](references/fr-10.md)** (~5,513 tokens)
  - Topics: Technical committee, Community contributing guide, Collaborators guide
- **[body and more](references/fr-11.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/fr-12.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/fr-13.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/fr-14.md)** (~7,935 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/fr-15.md)** (~3,084 tokens)
  - Topics: Additional examples, Comment puis-je structurer mon application, Comment puis-je définir des modèles

### General

- **[Fast, unopinionated, minimalist web framework forNode.js and more](references/general.md)** (~2,637 tokens)
  - Topics: Web Applications, APIs, Performance

### It

- **[API 3.x](references/it-1.md)** (~2,840 tokens)
  - Topics: Application
- **[API 4.x](references/it-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/it-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[Best practice sulla produzione: prestazioni e affidabilità and more](references/it-4.md)** (~7,398 tokens)
  - Topics: Things to do in your code, Operazioni da effettuare nellambiente  configurazione, Panoramica
- **[Aggiornamenti sulla sicurezza](references/it-5.md)** (~993 tokens)
- **[5.x API](references/it-6.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[Express con i proxy and more](references/it-7.md)** (~7,553 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Passaggio a Express 5 and more](references/it-8.md)** (~6,498 tokens)
  - Topics: Panoramica, Express 5 Codemods, Modifiche in Express 5
- **[Utilizzo del middleware and more](references/it-9.md)** (~7,965 tokens)
  - Topics: Middleware a livello dellapplicazione, Middleware a livello del router, Middleware di gestione degli errori
- **[Glossario and more](references/it-10.md)** (~6,657 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/it-11.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/it-12.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/it-13.md)** (~7,876 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/it-14.md)** (~2,965 tokens)
  - Topics: Additional examples, In che modo devo strutturare lapplicazione, In che modo è possibile definire i modelli

### Ja

- **[3.x API](references/ja-1.md)** (~2,814 tokens)
  - Topics: Application
- **[4.x API](references/ja-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/ja-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[実稼働環境におけるベスト・プラクティス: パフォーマンスと信頼性 and more](references/ja-4.md)** (~6,260 tokens)
  - Topics: コードで実行する処理, 環境セットアップで実行する処理, 非推奨バージョンや脆弱なバージョンの Express を使用しない
- **[5.x API](references/ja-5.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[プロキシーの背後の Express and more](references/ja-6.md)** (~5,283 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Express 5 への移行 and more](references/ja-7.md)** (~7,540 tokens)
  - Topics: Express 5 Codemods, Express 5 における変更点, 削除されたメソッドとプロパティー
- **[Contributing to Express and more](references/ja-8.md)** (~5,333 tokens)
  - Topics: Technical committee, Community contributing guide, Collaborators guide
- **[body and more](references/ja-9.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/ja-10.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/ja-11.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/ja-12.md)** (~7,720 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/ja-13.md)** (~2,410 tokens)
  - Topics: Additional examples, どのようにしてアプリケーションを構成するのですか, どのようにしてモデルを定義するのですか

### Ko

- **[3.x API](references/ko-1.md)** (~7,044 tokens)
  - Topics: express, Application, Request
- **[4.x API](references/ko-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/ko-3.md)** (~20,049 tokens)
  - Topics: express, Application, Request
- **[프로덕션 우수 사례: 성능 및 신뢰성 and more](references/ko-4.md)** (~6,524 tokens)
  - Topics: 코드에서 해야 할 일, 환경설정에서 수행할 항목, 더 이상 사용되지 않거나 취약성이 있는 버전의 Express를 사용 중지
- **[5.x API](references/ko-5.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[프록시 환경에서 Express 사용 and more](references/ko-6.md)** (~6,485 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Express 5로의 이전 and more](references/ko-7.md)** (~7,558 tokens)
  - Topics: Express 5 Codemods, Express 5에서의 변경사항, 제거된 메소드 및 특성
- **[Express와 함께 템플리트 엔진 사용 and more](references/ko-8.md)** (~6,518 tokens)
  - Topics: Technical committee, Express is made of many modules, Github Discussions
- **[body and more](references/ko-9.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/ko-10.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/ko-11.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/ko-12.md)** (~7,764 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/ko-13.md)** (~2,648 tokens)
  - Topics: Additional examples, 애플리케이션을 어떻게 구조화해야 합니까, 모델을 어떻게 정의해야 합니까

### Pt Br

- **[3.x API](references/pt-br-1.md)** (~2,841 tokens)
  - Topics: Application
- **[API 4.x](references/pt-br-2.md)** (~21,062 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/pt-br-3.md)** (~20,055 tokens)
  - Topics: express, Application, Request
- **[Melhores Práticas de Produção: desempenho e confiabilidade and more](references/pt-br-4.md)** (~7,693 tokens)
  - Topics: Itens a fazer no seu código, Coisa a se fazer no seu ambiente  configuração, Visão Geral
- **[Atualizações de segurança](references/pt-br-5.md)** (~1,007 tokens)
- **[5.x API](references/pt-br-6.md)** (~20,042 tokens)
  - Topics: express, Application, Request
- **[Express atrás de proxies and more](references/pt-br-7.md)** (~7,738 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[Migrando para o Express 5 and more](references/pt-br-8.md)** (~6,559 tokens)
  - Topics: Visão Geral, Express 5 Codemods, Mudanças no Express 5
- **[Usando middlewares and more](references/pt-br-9.md)** (~3,117 tokens)
  - Topics: Middleware de nível do aplicativo, Middleware de nível de roteador, Middleware de manipulação de erros
- **[Contributing to Express and more](references/pt-br-10.md)** (~5,512 tokens)
  - Topics: Comitê técnico, Community contributing guide, Collaborators guide
- **[body and more](references/pt-br-11.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/pt-br-12.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/pt-br-13.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/pt-br-14.md)** (~7,889 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/pt-br-15.md)** (~3,022 tokens)
  - Topics: Exemplos adicionais, Como eu devo estruturar meu aplicativo, Como eu defino modelos

### Zh Cn

- **[3.x API](references/zh-cn-1.md)** (~2,839 tokens)
  - Topics: Application
- **[4.x API](references/zh-cn-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/zh-cn-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[生产环境最佳实践：性能和可靠性 and more](references/zh-cn-4.md)** (~6,526 tokens)
  - Topics: Things to do in your code, 环境设置中的注意事项, 请勿使用不推荐或者存在漏洞的 Express 版本
- **[5.x API](references/zh-cn-5.md)** (~20,021 tokens)
  - Topics: express, Application, Request
- **[代理背后的 Express and more](references/zh-cn-6.md)** (~5,785 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[迁移到 Express 5 and more](references/zh-cn-7.md)** (~7,920 tokens)
  - Topics: Express 5 Codemods, Express 5 中的更改, 已移除的方法和属性
- **[Contributing to Express and more](references/zh-cn-8.md)** (~5,332 tokens)
  - Topics: Technical committee, Community contributing guide, Collaborators guide
- **[body and more](references/zh-cn-9.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/zh-cn-10.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/zh-cn-11.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/zh-cn-12.md)** (~7,716 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/zh-cn-13.md)** (~2,359 tokens)
  - Topics: Additional examples, 如何构造自己的应用程序, 如何定义模型

### Zh Tw

- **[3.x API](references/zh-tw-1.md)** (~2,839 tokens)
  - Topics: Application
- **[4.x API](references/zh-tw-2.md)** (~21,060 tokens)
  - Topics: express, Application, Request
- **[5.x API](references/zh-tw-3.md)** (~20,051 tokens)
  - Topics: express, Application, Request
- **[正式作業最佳作法：效能和可靠性 and more](references/zh-tw-4.md)** (~6,960 tokens)
  - Topics: Things to do in your code, 在環境  設定中的作法, 請勿使用已淘汰或有漏洞的 Express 版本
- **[5.x API](references/zh-tw-5.md)** (~20,038 tokens)
  - Topics: express, Application, Request
- **[位於 Proxy 背後的 Express and more](references/zh-tw-6.md)** (~5,157 tokens)
  - Topics: Cassandra, Couchbase, CouchDB
- **[移至 Express 5 and more](references/zh-tw-7.md)** (~7,763 tokens)
  - Topics: Express 5 Codemods, Express 5 中的變更, 已移除的方法和內容
- **[撰寫中介軟體以用於 Express 應用程式中 and more](references/zh-tw-8.md)** (~6,054 tokens)
  - Topics: Technical committee, Express is made of many modules, Github Discussions
- **[body and more](references/zh-tw-9.md)** (~6,097 tokens)
  - Topics: Installation, API, Errors
- **[cookie and more](references/zh-tw-10.md)** (~7,428 tokens)
  - Topics: Install, API, Examples
- **[Multer and more](references/zh-tw-11.md)** (~5,370 tokens)
  - Topics: Translations, Installation, Usage
- **[express and more](references/zh-tw-12.md)** (~7,774 tokens)
  - Topics: Installation, API, Session Store Implementation
- **[Express examples and more](references/zh-tw-13.md)** (~2,511 tokens)
  - Topics: Additional examples, 我該如何建立我的應用程式結構, 如何定義模型

## Usage Guidelines

1. **Identify relevant sections** - Match the user's question to the appropriate reference file(s)
2. **Load minimally** - Only read files directly relevant to the question to conserve context
3. **Cite sources** - Reference specific sections when answering
4. **Combine knowledge** - For complex questions, you may need multiple reference files

### When to use each reference:

- **2024**: 2024-related features and documentation
- **2025**: 2025-related features and documentation
- **De**: De-related features and documentation
- **En**: En-related features and documentation
- **Es**: Es-related features and documentation
- **Fr**: Fr-related features and documentation
- **General**: General documentation, overview, and getting started
- **It**: It-related features and documentation
- **Ja**: Ja-related features and documentation
- **Ko**: Ko-related features and documentation
- **Pt Br**: Pt Br-related features and documentation
- **Zh Cn**: Zh Cn-related features and documentation
- **Zh Tw**: Zh Tw-related features and documentation

Overview

This skill provides concise, practical documentation and guidance for using Express.js (versions 3.x–5.x). It consolidates core API usage, routing, middleware patterns, production best practices, and migration notes for 2024–2025 security updates. Use it to get clear, actionable answers for building and hardening Node.js web apps with Express.

How this skill works

The skill inspects Express API surface, routing and middleware conventions, error handling, request/response utilities, and deployment recommendations. It references security advisories and migration guidance across versions 3, 4, and 5, plus language-specific translations and best-practice sections for production readiness. Answers synthesize examples, configuration tips, and vulnerability mitigations from official docs and release notes.

When to use it

You need examples for routing, middleware, or error handlers in Express.
You are migrating an app between Express major versions (3→4 or 4→5).
You want production best practices for performance, reliability, or proxy configuration.
You need to address known vulnerabilities or apply security updates for 2024–2025.
You need language-specific guidance (de, en, es, fr) or translated documentation references.

Best practices

Use modular routers and middleware functions to keep routes composable and testable.
Handle errors with centralized error-handling middleware; avoid leaking stack traces in production.
Validate and sanitize inputs early (use body parsing and validation middleware) to reduce attack surface.
Configure trust proxy correctly when behind load balancers; set secure cookie and HSTS policies.
Keep dependencies updated and review security advisories for Express and common middleware (body-parser, cookie, basic-auth-connect).

Example use cases

Create a REST API with express.Router(), route parameters, and JSON request parsing.
Add authentication and session handling using cookie/session middleware with secure cookie options.
Migrate existing Express 4.x code to Express 5 using documented codemods and handle removed APIs.
Deploy Express behind a reverse proxy with correct trust proxy and logging for client IPs.
Implement global error handling that returns sanitized responses and logs internal errors.

FAQ

Which Express version should I use for new projects?

Use the latest stable 5.x release when your dependencies support it; it contains API refinements and long-term improvements. If you must remain on 4.x, follow migration guides and security advisories.

How do I protect an Express app in production?

Apply input validation, use HTTPS, set secure cookie and HSTS headers, configure trust proxy correctly, enable structured logging, and regularly update middleware to address CVEs and vulnerabilities.