Microsoft Teams app has an new architecture
The classic client of Microsoft Teams used open-source software such as Electron as the host, AngularJS as the web development framework, and a variety of custom controls constructed using HTML and CSS. When the development of Teams began in 2015, these choices enabled the rapid delivery of cross-platform web and desktop clients. However, as the capabilities and innovation of Teams expanded significantly over time, it placed strain on device resources. Recognizing this, the team began analyzing available technologies, benchmarking, building prototypes, and defining the new architecture known internally as the "north star". Key decisions made included participating and standardizing on the Fluent UI collection of UX controls, transitioning from Angular to React for building user interfaces, moving data processing out of the main thread to a client data layer worker, and lastly, transitioning from Electron to leverage WebView2 as the host.
The react based Fluent UI Web library is available as open source.