preview-versions

name	preview-versions
description	Preview documentation at a branch, commit or pull request without changing production. Use when debugging content on /tree/:branch, /blob/:sha or /pr/:number, or explaining how ISR and GitHub-pinned content work.

Preview versions

Content is served at request time. Production is pinned to a commit SHA; any branch, commit or pull request can be previewed through versioned URLs.

Mode	URL	Content
prod	/getting-started/introduction	pinned production SHA
tree	/tree/main/getting-started/introduction	latest commit touching the content directory
blob	/blob/<sha>/getting-started/introduction	immutable commit
pr	/pr/<number>/getting-started/introduction	the PR's head commit (follows new pushes)

Commit and PR previews are authorized: a /blob/ SHA must be in production history or belong to a PR (same-repo, or a fork PR carrying the preview:enabled label), and /pr/ applies the same rule. Unauthorized refs answer 404.

Raw markdown mirrors exist at /raw/** for production pages only — preview pages serve HTML.

Two cache tiers: ISR-cached page HTML at the edge, and a per-parser-version, per-content-SHA runtime cache for parsed Markdown bodies. A GitHub push to the production branch hits /api/revalidate and purges ISR.

Keyboard shortcut g h toggles the version-history panel on a docs page.

Read more: Architecture, Versioned previews.