Error Handling in Node.js and Express: Practical Best Practices

Unhandled errors crash servers and confuse users. Learn a clean, centralised approach to error handling in Express APIs.

Consistent error handling makes APIs predictable for frontend developers and easier to debug for you. Express supports a special error-handling middleware with four arguments.

A centralised error handler

class AppError extends Error {
  constructor(message, status = 500) {
    super(message);
    this.status = status;
  }
}

// Register after all routes
app.use((err, req, res, next) => {
  const status = err.status || 500;
  res.status(status).json({
    message: status === 500 ? 'Something went wrong' : err.message,
  });
});

Handling async route errors

Express 5 forwards rejected promises from async handlers to the error middleware automatically. In Express 4, wrap async handlers or call next(err) inside a try/catch.

Best practices

• Return meaningful HTTP status codes (400, 401, 403, 404, 409, 500)
• Never leak stack traces or internal details to clients in production
• Log errors with enough context to reproduce them
• Validate input early and return clear validation messages

• Node.js
• Express
• Error Handling