Preview deploy

A preview deploy is the per-PR live URL automatically created by deploy platforms (Vercel, Netlify, Cloudflare Pages, Railway) — lets reviewers see the actual rendered change before merge.

Preview deploys closed the loop on code review: instead of guessing how a PR looks, reviewers click a live URL. Implementations: deploy platform watches GitHub / GitLab, every PR triggers a fresh deploy at a unique URL (pr-123.preview.app), URLs are gated behind auth or password (or public for OSS), automatically torn down on merge. Combined with [[database-branching]], a preview deploy can also have its own ephemeral database. By 2026 preview deploys are table-stakes for Jamstack platforms; backend-only services still rarely have them (Render, Railway started adding them). Production patterns: comment from the deploy bot on the PR with the URL, automated Lighthouse / accessibility checks on preview, AI [[ai-code-review]] bots that pull preview screenshots.

When to use preview deploy

• Any frontend / full-stack PR workflow.

Common mistakes

• Leaving preview deploys public + indexable — duplicate-content SEO penalties, leaked drafts.

FAQ

Related terms

• Database branching — Database branching is the developer workflow where every PR / feature branch gets its own isolated database (copy-on-write of prod schema + sample data) — Neon, PlanetScale, Supabase, Turso ship branching as a flagship feature in 2026.
• Shadow deployment (LLM) — Shadow deployment runs a new model or prompt alongside the production one — receiving the same traffic but never showing output to users — to measure quality, latency, and cost before flipping live.

Last updated: 2026-06-01. Raw markdown: https://promtable.com/glossary/preview-deploy.md.