How to Set Response Headers in Express

Express' response object, commonly called res, has a set() function that sets a response header. For example, the following code sets the Content-Type header in an Express route handler.

app.get('/hello', function routeHandler(req, res) {
  res.set('Content-Type', 'text/plain');

  res.end('Hello, World');
});

To set a response header for multiple routes, you can use Express middleware. Just make sure you call app.use() to register your Express middleware before your route handlers.

// Sets `Content-Type` response header on *all** responses
app.use(function myMiddleware(req, res, next) {
  res.set('Content-Type', 'text/plain');
  next();
});

app.get('/hello', function routeHandler(req, res) {
  // `myMiddleware` already executed when `routeHandler` runs
  res.end('Hello, World');
});

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