That statement's horribly misleading. The desktop versions (eg. windows or mac) aren't, but the web versions are.

No, it's not misleading. The Office 365 desktop apps are written in React. As is Teams. As is Visual Studio Code.

Specifically, React Native for Windows. https://github.com/Microsoft/react-native-windows

For things like background services, they still use C/C++.

> No, it's not misleading. The Office 365 desktop apps are written in React. As is Teams. As is Visual Studio Code.

Is there a source for this? I searched around and can only find rumors from 2018, and announcements that the mobile apps are using react.

You're right that the main source is a 2018 original tweet, and then some articles building on that tweet, and then news dries up.

This is the best I can find, with the Microsoft MVP clarifying the situation:

https://mspoweruser.com/no-microsoft-is-not-rewriting-office...

Specific point of interest:

"Office 365’s UI, a lot of it, but definitely not all of it, are pieces that are built using React Native (Windows). API’s and Services are still going to be powered by C++, C#, or whatever is the most appropriate for that team. Nothing is converting to “all/completely” JavaScript/TypeScript."

To me, this confirms that at least the UI is React. Anecdotally, it feels very "web" as I use it daily. Sluggish, missing paint cycles when switching between apps, and the typical main thread freezes.

I'll let you decide if this is convincing enough evidence :)