Adding Steam Workshop Addons and Collections

How Workshop Addons Work

GMod servers load Workshop addons from a Steam collection. When the server starts, it downloads any addons in the collection that are not already cached, then sends the addon list to connecting clients so they can download the same content.

Workshop cache is stored at:

garrysmod/cache/workshop/

Getting Your Collection ID

1. Create a Steam Workshop collection at steamcommunity.com/workshop/browse/?appid=4020
2. Add all desired addons to the collection and set it to public
3. The collection ID is the numeric portion of the URL: steamcommunity.com/sharedfiles/filedetails/?id=<ID>

The collection must be public. Private collections cannot be downloaded by the server.

Steam Web API Key

Workshop downloads require a Steam Web API key alongside the collection ID. Obtain one at steamcommunity.com/dev/apikey. The key is tied to your Steam account.

Configuring in Pterodactyl

Set these startup variables in your panel:

If your egg does not have a dedicated API key variable, add -authkey <key> directly to the startup command line in the panel.

Manual Launch Flags

+host_workshop_collection 1234567890 -authkey YOURAPIKEY1234567890ABCDEF

Both flags must be present together. The collection flag without the authkey causes Workshop download timeouts.

Forcing Client Downloads with Lua

Workshop collections handle server-side downloading, but clients connecting mid-session may not automatically download all addons. To force clients to download a specific addon, add a Lua file:

garrysmod/lua/autorun/server/workshop.lua

With content such as:

-- Force clients to download specific Workshop addons
resource.AddWorkshop("123456789")
resource.AddWorkshop("987654321")

The string passed to resource.AddWorkshop is the addon's numeric Workshop ID. This is different from the collection ID — it is the ID of each individual addon within the collection.

Finding Individual Addon IDs

Navigate to the addon's Workshop page. The ID is in the URL:

steamcommunity.com/sharedfiles/filedetails/?id=123456789
                                                ^^^^^^^^^
                                                This number

Adding New Addons

1. Add the addon to your Workshop collection on Steam
2. Restart the server — Workshop addons do not hot-reload
3. Clients will be prompted to download on next connection

If an addon update breaks your server, temporarily remove it from the collection and restart. The cached version in garrysmod/cache/workshop/ will no longer be used once removed from the collection.

Addon Load Order

Addons load alphabetically by folder/addon name. If one addon depends on another (e.g., ULX depends on ULib), ensure ULib's name sorts before ULX alphabetically, or use explicit dependency handling in Lua. ULib (557962238) and ULX (557962280) are designed to handle this automatically when both are in the collection.

Troubleshooting Workshop Downloads

Timeout on startup:

• Verify -authkey is set and the key is valid
• Confirm the collection is set to public
• Check outbound UDP ports 27020, 26901, and 1200 are open

Addons not appearing in-game:

• Confirm the collection ID matches the one in your launch flags
• Check garrysmod/cache/workshop/ — files should appear after restart
• Look for download errors in the startup console output

Related

• Installing Your Garry's Mod Dedicated Server
• Installing and Using ULX and ULib Admin Mod
• Understanding Lua Scripting and Addon Structure
• Troubleshooting Common Garry's Mod Server Errors