Garry's Mod: gamemodes, addons, and Workshop content

A Garry's Mod server comes down to three things: the gamemode it runs, the addons you load, and server.cfg. The key trick is loading addons from a Steam Workshop collection so players auto-download them on join.

Set the gamemode and map

The gamemode is set with launch parameters on the Startup tab:

+gamemode sandbox +map gm_construct +maxplayers 16

Common gamemodes: sandbox, darkrp, terrortown (TTT), prop_hunt. The gamemode's folder must exist in garrysmod/gamemodes/ — Workshop addons can add gamemodes (see below). Set a matching starting map (e.g. rp_downtown_v4c for DarkRP).

Load addons via a Workshop collection (recommended)

The clean way to run addons is a Steam Workshop collection — players auto-download everything when they connect.

1. On Steam, create a Workshop collection and add every addon you want.

2. Copy the collection's ID from its URL.

3. On the Startup tab (or in server.cfg), set:

   host_workshop_collection YOUR_COLLECTION_ID
   

4. You also need a Workshop authentication key (+gmod_workshop_id/-authkey depending on setup) for reliable downloads — generate one at Steam's Web API key page and add it as the server's workshop auth key.

5. Restart. The server downloads the collection on boot (first start takes longer).

Manually-installed addons also work: extract them into garrysmod/addons/<addon>/, but Workshop collections are easier to keep in sync with clients.

Fast download (sv_downloadurl)

Without it, players download custom maps/content slowly through the game server. Point sv_downloadurl at a web host serving your content for much faster joins:

sv_allowdownload 1
sv_downloadurl "https://your-fastdl-host/gmod/"

Set this up once you have custom maps that aren't on the Workshop.

Configure server.cfg

Edit garrysmod/cfg/server.cfg in the File Manager:

hostname "My ServerPrism GMod Server"
rcon_password "a-strong-password"
sv_password ""
sbox_maxprops 200
sv_lan 0

• hostname — server browser name.
• rcon_password — remote admin via rcon from the in-game console.
• sv_password — set to make the server private.
• sbox_maxprops and other sbox_* limits — tune to prevent prop spam / lag in sandbox.

Save and restart, or exec server.cfg from the console.

Common issues

• Players stuck downloading / missing textures: Workshop auth key not set, or the collection is private — make it public and set the key.
• Gamemode won't load: the gamemode folder isn't present — it must be a Workshop addon or extracted into gamemodes/, and +gamemode must match the folder name.
• Addons work for you but not others: they were installed manually server-side only — use a Workshop collection so clients get them too.
• Server not in browser: sv_lan must be 0.