Fix GMod "Map Differs From Server"

When a player is kicked with "Your map differs from the server's", the map file on their computer is not the same file your server is running. Facepunch's wiki doesn't describe this kick by name, so this guide combines what its Workshop pages say with the one matching report on its issue tracker. Treat the causes below as things to check, in order, rather than a guaranteed diagnosis.

What the one Facepunch report says

Facepunch's issue tracker has an open report of this kick. A map in a Workshop addon was updated under the same name, and players who were not subscribed to that addon were kicked with the "differ's from the server's" message. The report says it happens whether or not the map is in the server's collection or marked with resource.AddWorkshop. When an affected player subscribed to the addon by hand, the problem went away for them. The report is still open. A Facepunch developer asked whether it could be reproduced, and the reporter had not reproduced it on demand, so there is no confirmed cause.

Other things to check

• Your server may be on an older version of the map. Facepunch's Workshop guide warns that turning off automatic updates can leave your server on an older version of a map, which can stop players joining. A server like yours updates the addons in its collection when it starts, unless you changed that yourself in server.cfg.
• A map that came from outside the Workshop. Facepunch's guide to serving content says downloads outside the Workshop, such as FastDL, are not checked for their contents, so updating a file on the server does not make a player's game fetch it again. We don't host FastDL, so the Workshop is the route for getting a map to your players.

On the server

1. Open the Startup tab and check Map. It has to match the file name without the ending: gm_construct for gm_construct.bsp.
2. If the map is part of your Workshop collection, open the Workshop tab. A row marked Update waiting: restart to download means Steam has a newer version than the server has. Restart the server from the Console tab so it picks that version up.
3. Watch the Console as the server starts. For a map that is in your collection, Facepunch's wiki says the server marks it for players to download and prints Making workshop map available for client download. If that line never appears, check that the map is in the collection and that its file name matches Map.

For a map that is not on the Workshop yet, publish it there and add it to the collection, as How to add a Steam Workshop collection to your GMod server describes.

For the player

1. Have the player open the map's Workshop page on Steam and press Subscribe.
2. Let Steam finish downloading, then rejoin. In the Facepunch report, subscribing made the problem go away for the affected player.

If it keeps happening

Open a support ticket with the map's file name, its Workshop link and the lines from the last boot in the Console. The exact map name and what changed just before the first kick are what help most.