[OS] Platform ids are used primarily by the brainCloud Authenticate() calls, to track the usage of your app by platform.
The list of platform strings is defined in the Appendix section of the API Reference.
Most of the client libraries have constants for each of the platforms (and the Unity library figures it out automatically). However, when using the API explorer, you will need to fill in the platform manually.
Important note #1 - you use the design portal to configure which platforms your app will allow. You configure this from the Design | Core App Info | Platforms page.
Important note #2 - brainCloud uses a separate set of Store Platform Ids to identity the various AppStores. You'll find a list of those here.
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