Where is the official GitHub Pages custom-domain documentation?

The URSY truth-spine source for GitHub Pages is https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/managing-a-custom-domain-for-your-github-pages-site. Check the live page before making production DNS changes.

Source checked 11 August 2026: GitHub Pages official documentation.