How can I test a Vercel deployment without letting the public access it?

Protecting the URL is only part of the solution. Use a separate database, API keys, storage, and email catcher for staging so test signups, orders, and emails cannot affect real users. Preview deployments generally are not indexed by search engines, but authentication is still needed to stop someone who discovers or guesses the deployment URL.

The usual approach is to create a staging or preview deployment that mirrors production, then protect it with Vercel Authentication or password protection. Only you and your team can access it, while the public production deployment stays separate. A normal workflow is development locally, then staging, and finally production.