Wide GitHub от fabiocchetti

Wide GitHub is a Firefox extension that expands GitHub’s layout, enhancing readability, reducing vertical scrolling, and improving accessibility.

It works on GitHub, private Gists, GitHub Enterprise, and custom domains (Firefox 109+ required for custom TLDs support).

Use the settings panel to manually add the URL of your custom domain where GitHub is being hosted (i.e. git.​mycompany.​com).