How do I install an addon that is not on the Steam Workshop?
For addons sourced from GitHub or distributed as a ZIP rather than published to the Workshop, install them via File Manager instead of Addon Manager.
Extract the addon locally first and confirm it has the right structure: a proper GMod addon has a lua/ folder (or an addon.txt file) at its root, not buried inside another folder. Upload the whole addon folder to garrysmod/addons/ via File Manager, then restart the server.
For larger addons, SFTP (using a client like FileZilla or WinSCP) is faster than the browser file manager for bulk uploads.
If you are only installing something with a GitHub repository URL, check whether Addon Manager supports pasting that URL directly first; it handles the folder structure for you and is usually less error-prone than a manual upload.
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