Catch missing keys before your deploy fails

A deploy that fails on a missing key costs you a build and a session reading logs. This check compares the environment variable names your app requires with a local configuration, so you see what is missing before you deploy.

It compares names only. It never prints secret values, and it does not verify that a credential is valid or upload any values to your host. Set the actual secrets in the host's environment configuration, and keep server credentials out of public-prefixed variables.

It is part of the deploy preflight for Vercel or Railway in the Deploy your first app and verify the live result guide. It runs locally from the command line with Python 3.10 or later, on Windows, macOS and Linux. Hosting and provider charges are separate and not included.