Vercel Env Checker

Next.js / Vercel env debug wizard

Debug missing Vercel environment variables.

Find why a Next.js env variable is undefined, stale, or missing in production. Get a prioritized checklist, safe commands, and a debug snippet that does not print secret values.

Describe the failure

No secrets needed
Do not paste API keys, tokens, passwords, database URLs, or real environment variable values into this tool.

Most likely causes

critical

The browser cannot read a server-only variable

Next.js does not expose non-public environment variables to browser code.

  • Do not add NEXT_PUBLIC_ to a secret. Move the read to an API route, route handler, server component, or backend service.
  • Confirm the failing code is really running in the browser.
warning

The value may be configured in the wrong Vercel environment

Vercel has separate Production, Preview, and Development environment scopes.

  • Open Vercel Project Settings > Environment Variables.
  • Confirm the value exists for Production deployment.
  • If the value was added after the deployment, redeploy the target environment.

Safe commands

vercel env ls
vercel env pull .env.local
vercel --prod

Safe debug snippet

const value = process.env.MY_ENV_VAR;

console.log({
  name: "MY_ENV_VAR",
  exists: Boolean(value),
  length: value?.length ?? 0,
});

// Do not log the raw value.

What this checks

The checker covers common Next.js and Vercel environment variable mistakes: browser access, `NEXT_PUBLIC_`, production versus preview scope, redeploy timing, local sync, and safe debugging.

What this does not do

It does not connect to your Vercel account, inspect your repository, read secret values, or guarantee that a deployment is production-ready.

Official references

Next.js environment variablesVercel environment variables

Common cases

Why is my variable undefined in the browser?

In Next.js, browser-exposed values need the `NEXT_PUBLIC_` prefix. Do not use that prefix for secrets.

Why do I still see the old value?

Public client values are bundled at build time. Change the value, create a new deployment, and confirm production points to it.

Why does local work but Vercel fails?

Your local `.env.local` and Vercel project environments may not match. Pull Vercel env values locally and restart the dev server.