Why must application environment variables be updated after changing domains?

Why must application environment variables be updated after changing domains?

Environment variables need updating after a domain change when they contain values tied to the old address. Not every variable changes. Database credentials, for example, usually remain unrelated to the public hostname unless the migration also changes the underlying service.

Identify where the old address is used

An application may store its public base URL in configuration and use it to build invitation or password-reset links. Authentication libraries may also depend on an external URL, trusted host, or callback configuration.

Search the code and deployment settings for the old hostname and trace how each occurrence is used. For a wedding app, confirm that newly generated invitation links lead guests to the custom domain rather than the earlier deployment address.

Update related provider settings consistently

Some domain dependencies live outside environment variables. An identity provider may require an exact redirect URL, and a storage service may restrict browser requests to approved origins. Update those settings through the appropriate provider configuration.

Review cookie domain settings only if the application sets them explicitly. Avoid broadening cookie access merely to make a migration appear successful. Keep development, preview, and production values aligned with the environment they actually serve.

Deploy and verify the complete flow

On Vercel, changing an environment variable applies to new deployments, so deploy the intended release after saving the production settings. Vercel's environment-variable documentation describes this behavior.

Test login, logout, a controlled invitation, and any photo upload performed from the new origin. Inspect the resulting URLs without exposing secrets in logs. Record which values changed and why. A successful domain migration means the application generates and accepts the right addresses throughout its workflows, not simply that its homepage opens at a new name.