Fix Vercel 500 Internal Server Error in a Next.js Deployment
A Vercel 500 usually means the app built successfully but crashed at runtime. Start with Function Logs, missing environment variables, and API route/server action exceptions.
The local app works, but the deployed URL returns 500.
The Vercel build is green, yet a route or API endpoint fails.
The browser only shows Internal Server Error without useful details.
What to check first
Platform: Vercel Error: 500 Internal Server Error after deploy
A Vercel 500 usually means the app built successfully but crashed at runtime. Start with Function Logs, missing environment variables, and API route/server action exceptions.
Step-by-step fix
Open Vercel ? Project ? Deployments ? latest deployment ? Functions or Runtime Logs, then copy the first real stack trace.
Check that every required environment variable exists in Vercel for the correct environment: Production, Preview, or Development.
Look for server-only imports, file-system reads, database clients, or API routes that work locally but fail in a serverless/runtime environment.
Wrap the failing API route or server action in a temporary try/catch and log a narrow error message, then redeploy.
# Local parity check before redeploy
npm ci
npm run build
npm start
# Common fix: add missing env vars in Vercel Project Settings ? Environment Variables
Common mistake to avoid
Do not keep redeploying blindly. If the build passed, the useful evidence is usually in runtime logs, not build logs.
Still stuck?
Send the deploy log, repository link, target platform, and expected URL. ShipFast Deploy Rescue is a fixed-price debugging service for indie projects and MVPs.