Environment Variables Not Loading - Undefined in Build
Environment variables are undefined in your deployed application even though they're set in the platform. API keys, database URLs, and other config values come back as undefined.
Variables work fine locally but disappear after deployment.
Error Messages You Might See
Common Causes
- Using process.env.VAR instead of NEXT_PUBLIC_VAR for client-side access
- Environment variables set after build completes
- Wrong environment selected in deployment platform (staging vs production)
- Variable name mismatch between code and platform settings
- Quotes or special characters in env var value causing parsing issues
How to Fix It
For client-side vars: prefix with NEXT_PUBLIC_ (e.g., NEXT_PUBLIC_API_URL)
For server-side only: use plain process.env.PRIVATE_VAR (won't leak to browser)
Set env vars BEFORE triggering redeploy in your platform
Test locally: create .env.local with same vars and run npm run build
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Get HelpFrequently Asked Questions
What's the difference between .env and .env.local?
.env is version controlled, .env.local is git-ignored. Use .env.local for secrets locally
How do I set env vars in Vercel?
Settings > Environment Variables. Make sure you set them before deploying
Should secrets use NEXT_PUBLIC_?
NO! Use NEXT_PUBLIC_ only for public values. Secrets stay as plain process.env.VAR and are only available on server