Staging, preview and production

Production is the live app that real customers use. Staging is a copy set up as close to production as possible, with its own database, keys and test payment accounts, where a release is checked before it goes out. Preview deployments are short-lived copies built for each pull request, each at its own URL, so a reviewer or client can click through a change before it is merged.

Vercel, Netlify and Cloudflare Pages create previews automatically. The environments differ mainly in their environment variables, and keeping them apart matters: a staging site pointed at the production database, or test emails sent to real customers, are classic accidents. Previews of unfinished work are best kept out of search engines, and behind a password where needed.