Documenting the unofficial and internal Steam Web API
This wiki is not intended to list or document any "official" API that typically use an API key. If you are interested in that, I recommend this lovely Steam Web API Documentation by @xPaw.
WE NEED YOUR HELP!
Because of the nature of this kind of API, we desparately seek contributions to the wiki to keep the documentation up-to-date and complete!
If this documentation was helpful to you in any way, please consider taking a few minutes to add a new wiki entry or update an existing one (look out for TODO). Also, a ☆ Star is much appreciated!
This JavaScript script may help you generate a proposal of the API documentation of an endpoint. Unfortunately, it is not able to detect variables (such as appids and steamids), you have to correct this manually.
Most of these unofficial API endpoints can be found by reverse engineering. Check out this tutorial by @Google.
There are also other sources that are tracking them (undocumented), here are a few of them: