[▲ Vercel Community](/) · [Categories](/categories) · [Latest](/latest) · [Top](/top) · [Live](/live) [Feedback](/c/feedback/8) # Preflight OPTIONS error despite correct CORS configuration 59 views · 0 likes · 1 post Thomas94170 (@thomas94170) · 2025-08-12 Hello everyone, I’m currently facing an issue when deploying a NestJS API on Vercel: **Preflight OPTIONS** requests consistently fail (401/403/405) even though: * CORS is properly configured in `main.ts` (`origin`, `methods`, `allowedHeaders`, `credentials`). * The `OPTIONS` routes correctly return a 204 with all required `Access-Control-Allow-*` headers. * The routes have been allowed in `vercel.json` (for example `/auth/*`). * I have temporarily disabled all security measures (auth middlewares, validations) to test, but the issue persists. **Context:** * Deployment on Vercel (`api/index.ts` properly set up to handle preflight) * Cross-testing local ↔ staging: works fine locally, fails on Vercel * This strongly appears to be an internal Vercel issue (support ticket already opened) **My question:** Has anyone encountered this issue before? Do you know of a solution or workaround to make OPTIONS requests pass correctly on Vercel in this scenario? Thanks in advance for your feedback! 
