GitHub Pages

"records": { "CNAME": "you.github.io" }

Replace you with your GitHub username or org, exactly as it appears in your Pages URL.

Two ways to apply this. The quickest is runs-at.dev/manage: sign in, pick the record type, paste the value, save. It writes the same commit to the registry and DNS follows within seconds. The steps below do it by pull request instead, which is what you want if you would rather review the change first. Either way handles subdomains entries.

1. Fork the registry and edit domains/you.json to the record above.
2. Open a pull request. Once merged, the CNAME is synced to DNS automatically.
3. In the Pages repo itself, add a file named CNAME at the repo root containing a single line, you.runs-at.dev. This is GitHub's own custom-domain mechanism, independent of the registry, and Pages will not serve the custom domain without it.
4. In the repo's Settings → Pages, the custom domain field should show you.runs-at.dev (GitHub reads it from the CNAME file once pushed). Enable "Enforce HTTPS" once the certificate is issued.

Order matters less than you'd think here: the registry PR and the Pages CNAME file can land in either order, GitHub just won't issue a certificate until both point at each other.

Settings → Pages shows "DNS check successful" once GitHub confirms the CNAME. Visiting https://you.runs-at.dev should then serve the Pages site.