Works Locally, Fails in Production
Problems that only appear after deploy — env, build, CORS, and runtime differences.
Cross-topic section
This view references problems owned by primary sections — no duplicate records. Owned by: Next.js, Django / Flask / FastAPI, Docker, Supabase / Firebase, Deployment / Production-Only Problems.
Next.js hydration error appears only after production build
Next.js environment variable works locally but is undefined after deployment
Next.js page works locally but returns 404 in production
Next.js image loads locally but fails after deployment
FastAPI CORS works locally but fails after deployment
Flask app works locally but returns 502 behind Nginx
Supabase OAuth redirect works locally but fails in production
Application works locally but fails immediately in production
Production database connection fails while manual connection works