Their own custom framework built on top of Win32, nowadays they also use React Native, and Webview2 with React to share code with the Web versions.

The Web versions also consume C++ via WebAssembly, the mobile versions are a mix of the platform languages + C++.

There are some CppCon talks about how they use C++ in Office.

> Webview2 with React to share code with the Web versions.

In a complicated Excel sheet I had the Conditional Formatting Rules Magaer crash due to an issue in EmbeddedWebView2.dll. Renaming it helped preventing the crash without obvious decline in functionality in Excel, until I tried to join a Teams meeting which obviously uses WebView2.

Building apps on Windows feels like a big PITA to get into. The amount of different frameworks and libraries to work with is perplexing to a new developer and I really do not want to use electron or React or even Qt.

Where do I start? Do you have a compiled version of some information on this?

You start by using the Qt installer, and installing QtStudio alongside mingw, hardly that complicated for anyone that has ever done C or C++ development.

Since I know those languages since 1992, and have coded for Windows since Windows 3.0, I never bothered with any guide personally.

Even following their own "getting started" tutorials you get stuck at step one trying to find Visual Studio or whatever it's called nowadays.

Oh, you mean Visual Studio 2026 Copilot App 365 & Knuckles?

> Where do I start?

I hate to say but GitHub Copilot can get you started. It slurped up all of Microsoft SDK and docs and open source libs. It is a decent reference.

I'm also kinda impressed by the Debugger Agent [0] built into Visual Studio 2026.

[0] https://medium.com/@onu.khatri/copilot-squad-in-vs-2026-ca88...