Do I need to redeploy after adding a Vercel environment variable?

Yes, always. Vercel injects environment variables at build time. Adding or changing a variable in the dashboard has no effect on live deployments until you trigger a new deployment. Redeploy from the dashboard or push a commit.

How do I check what environment variables are available in my Vercel function?

Add a temporary log: console.log(Object.keys(process.env)) or console.log(process.env.YOUR_VAR_NAME). Deploy and check the function logs in Vercel Dashboard > Functions > your function > Logs. This shows exactly what's available at runtime.

Why is my Vercel env variable undefined in the browser but defined server-side?

Client-side code in Next.js can only access variables prefixed with NEXT_PUBLIC_. Server-side code (API routes, getServerSideProps, server components) can access all variables. Add the NEXT_PUBLIC_ prefix and redeploy to make a variable available in the browser.

Vercel · Problem Fix

Vercel Environment Variable Not Loading

You added the env variable in the Vercel dashboard but it's still undefined in your function. This is almost always a redeploy requirement or environment scope mismatch — not a Vercel bug.

1. You added the variable but didn't redeploy

Vercel bakes environment variables into the build at deploy time. Adding a variable in the dashboard does NOT update a live deployment. You must trigger a new deployment after adding or changing env vars. Go to Deployments > Redeploy, or push a new commit to trigger a build.

2. Variable is scoped to wrong environment

Vercel has three environments: Production, Preview, and Development. A variable set for 'Preview' is not available in 'Production' deployments. Check your variable's environment scope in Settings > Environment Variables and ensure it's set for the environment you're deploying to.

3. Variable name has a typo or wrong case

Environment variable names are case-sensitive. NEXT_PUBLIC_API_KEY and next_public_api_key are different variables. Copy-paste the exact name from your code and the dashboard side-by-side to verify they match character for character.

4. Missing NEXT_PUBLIC_ prefix for client-side variables

In Next.js on Vercel, variables available in the browser must be prefixed with NEXT_PUBLIC_. Without this prefix, the variable is only available server-side. If your client code is reading undefined, check whether you need the prefix.

5. Variable shadowed by .env file in the build

If your repository has a .env or .env.production file committed, its values override Vercel dashboard settings during build. Check your repo for .env files and ensure they don't contain conflicting or empty values for the variable you're trying to set.

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