Question 1

Why does my Garry's Mod server not download all the Workshop addons?

Accepted Answer

The server downloads a collection item by item and gives up on an item that takes too long, so the failure is size-driven: small addons arrive and one large one does not. The log shows "Timed out!" or "Error! Failed to read the downloaded file". Splitting the biggest items out of the collection, or mounting them as fast-download content instead, is what fixes it rather than restarting.

Question 2

How do I make players download my server's addons?

Accepted Answer

host_workshop_collection makes the SERVER mount the collection. It does not make clients download anything. For that each addon needs a resource.AddWorkshop line in a Lua autorun file, or the content has to come from a FastDL host. A collection that mounts fine server-side and still shows missing textures to players is almost always this.

Question 3

How large can a Garry's Mod Workshop collection be?

Accepted Answer

There is no published hard limit, but the practical one is join time: everything a client must download before it can spawn. A collection over roughly 1 GB makes a first join slow enough that players leave, and individual items over about 100 MB are the ones that most often fail to download server-side.

Question 4

Does the collection ID go anywhere?

Accepted Answer

The lookup is relayed through this site's server to Steam's public API, because Steam's API does not accept requests from browsers. Nothing about the collection is stored, and the results go only back to your page.