Where's this data obtained from?

Servers data are obtained directly from the Steam API. GoldStats doesn't perform UDP port scanning/queries for statistics (As of 2025-03-08, GoldStats is now querying GoldSrc servers ONLY for data related to server variables).

How does this works?

It's just a Lua script that runs each day automatically with a cronjob (at 03:00 UTC) and it returns all obtained data as a JSON output which is then processed by PHP. Yes I know, very archaic but I don't care.

Why on some games like Counter-Strike the server counter says "10000+"?

This is due to a limitation with the Steam API which appears to have a limit of 10,000 servers (even if you add a high limit on the GET it still returns 10,000).

What does "(old)" means on some games?

If refers to those GoldSrc mods which already has a Steam standalone version but are using the legacy Half-Life mod format (in other words, installed from Half-Life folder and running inside Half-Life's Steam AppID 70). Mainly because there are people playing old versions of mods like Sven Co-op 3.0.

Is this 100% accurate?

No. The vast majority of servers are usually fake (aka redirects servers which tends to spam the master server, mostly on Counter-Strike), the limit of servers returned by the API that prevents us from getting a real count and players who may also be bots or HLTVs.

There are some mods that are not listed here

I'm aware of that.

Why you created this?

Just out of curiosity and to see who also plays forgotten GoldSrc mods rather than those generic and most known GoldSrc-based games like CS and TFC.

Would you make something like this but for Source games?

I would like but I'm not interested on doing that.

Does Xash3D FWGS servers also counts here?

At this moment, no.