Fix: Cannot set headers after they are sent to the client
Fix Node.js/Express 'Cannot set headers after they are sent to the client', usually a missing return, double next(), or a duplicate response.
Tag: express
5 articles
RSSFix: Express Middleware Not Working — Order Wrong, Errors Not Caught, or async Errors Silently Dropped
How to fix Express middleware issues — middleware execution order, error-handling middleware signature, async error propagation with next(err), and common middleware misconfigurations.
Fix: Express Rate Limit Not Working — express-rate-limit Requests Not Throttled
How to fix Express rate limiting not working — middleware order, trust proxy for reverse proxies, IP detection, store configuration, custom key generation, and bypassing issues.
Fix: Express req.body Is undefined
How to fix req.body being undefined in Express — missing body-parser middleware, wrong Content-Type header, middleware order issues, and multipart form data handling.
Fix: CORS Not Working in Express (Access-Control-Allow-Origin Missing)
How to fix CORS errors in Express.js — cors middleware not applying, preflight OPTIONS requests failing, credentials not allowed, and specific origin whitelisting issues.