This question comes up from time to time. Customers want to build a custom client for Teams.
- I love Teams, but our corporate colour is green not blurple, can we make a client that is green
- We want build a Teams client with just chat, can we do that?
The answer is no, you can’t build your own client. Teams is build on various cloud micro services and Microsoft do not expose public API’s to the services, so even though its all http. There are no API’s and no documentation for how to build your own client. Technically you could try and sniff it and reverse engineer it, but you have to bear in mind that changes to the service and clients are frequent. What you found worked today may not work tomorrow.
So if you want Teams, the Microsoft clients are your only option. Microsoft really want a ‘consistent experience and UI’ across web, desktop (windows and mac), mobile and devices (MTR and Phones).
This is different to Skype for Business where you could run the Skype for business client in a hidden UI surpressed mode, where you could leverage the client to do the heavy lifting but be hidden, and build your application on top, for example building a Kiosk client. Some people also built genuinely custom clients, for example for Linux. Also 3PIP phones were essentially third party written (and certified and approved) SfB clients.