Vercel Environment Variables Not Loading in Deployment
Your application builds successfully but environment variables aren't available at runtime in Vercel. Features depending on env vars fail in production, though they work in local development.
Environment variables don't load in Vercel when they're not properly configured in project settings, use incorrect naming conventions, or are set for wrong deployment environments.
Error Messages You Might See
Common Causes
- Environment variables not added to Vercel project settings (must be set in UI, not just .env)
- Variables set for wrong environment (e.g., production-only but accessing in preview deployment)
- Using .env file instead of Vercel Settings, and .env not committed (ignored by git)
- Variable names not prefixed with NEXT_PUBLIC_ for client-side access
- Redeployment not triggered after changing env vars, using cached build
How to Fix It
Set in Vercel UI: Go to Project Settings > Environment Variables. Add each variable for Production, Preview, Development as needed.
Restart deployment: After changing env vars, trigger new deployment: push to git or click 'Redeploy' button in Vercel.
Client-side vars: Prefix with NEXT_PUBLIC_: NEXT_PUBLIC_API_URL=https://api.example.com
Server secrets: Don't prefix secrets: DATABASE_URL=postgres://... keeps them server-only.
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Get HelpFrequently Asked Questions
How do I add environment variables in Vercel?
Go to project > Settings > Environment Variables. Add each variable, select which environments (Production, Preview, Development) it applies to.
Should I commit .env file to git?
Never commit secrets. Commit .env.example with placeholder values. Use Vercel UI for actual secrets.
Why is API_KEY undefined in production?
Check 1) Variable set in Vercel Settings 2) Correct environment selected (Production vs Preview) 3) Deployment restarted after adding variable.