OpenAPI specification for Steam's Web API. You can read our full guide to learn more about the Steam Web API
The public spec refers to API endpoints that can be accessed by anyone with a key, as documented here.
Get your API key from here.
Try the API in the Zudoku Playground
The partner spec is for "partner only" APIs that are reserved for Steam partners/publishers, as documented here.
Learn how to get your API Key from here.
Try the API in the Zudoku Playground
Unpublished/hidden API endpoints as enumerated here. That page is the best way to read about and test those APIs.