Microsoft's Windows App SDK Set for Open Source Future — Here's What to Expect

Microsoft has published an article on Github detailing its plans to open source the Windows App SDK. Beth Pan, a software engineer on the Windows App SDK team at Microsoft, announced the plans in a post on GitHub late last week.

In the post, Pan confirms that there is an intention to begin moving the Windows App SDK towards a more open and collaborative future, and that plans for truly open sourcing the repo are being made, but that no specific time frame has been committed to.

"Many of you have asked about truly open sourcing the repo. While we’re not ready to commit to a specific end date for completing all milestones, we are actively working toward it. This isn’t a flip-the-switch moment, it’s a deliberate process," says Pan.

The reason for this is how deep WinUI and the Windows App SDK runs in Windows. Parts of the codebase reach into proprietary layers of the OS, much of which is not permitted to being open sourced. As such, the Windows App SDK team needs to decouple the things that can be open sourced from the bits of Windows that can't.

Pan continues, "We are being thoughtful about resourcing. This effort is happening alongside other critical responsibilities like security, platform stability, and support for existing products. Our current focus is on foundational work that unlocks value for contributors and increase transparency. We are aligning this work with Microsoft’s broader business priorities to ensure long-term support and impact."

It appears there are four key phases that need to be reached before Microsoft can move ahead with a true open-sourcing of the Windows App SDK. These phases will take place over the next 6+ months, the company has confirmed.

• Phase 1: Increased Mirror Frequency
  After the WASDK 1.8 release (end of August), we’ll begin more frequent mirroring of internal commits to GitHub to increase transparency and show progress.
• Phase 2: 3rd Party Devs Build Locally
  External developers will be able to clone and build the repo locally, with documentation to guide setup and dependencies.
• Phase 3: 3rd Party Devs Contribute & Run Tests
  Contributors will be able to submit PRs and run tests locally. We’re working to untangle private dependencies and make test infrastructure publicly accessible.
• Phase 4: GitHub as Center of Gravity
  GitHub becomes the primary place for development, issue tracking, and community engagement. Internal mirrors will be phased out.

So, while work to open source the Windows App SDK has been confirmed, we're likely still a long way off from it actually happening. With that said, this is something to look forward to if you're a Windows app developer looking to help improve the Windows App SDK.

In recent months, many developers have worried that the Windows App SDK was being abandoned by Microsoft. Key issues and concerns were not being addressed, and it had been a while since any meaningful updates were added to the kit.

But the announcement that the company will eventually open-source it has given developers a new wave of hope. Hopefully we'll see continued investment in the SDK over the next few years, as there are still many issues and ideas that developers would like to see fixed and included.

In the meantime, what are your thoughts on the Windows App SDK and WinUI 3? Should Microsoft invest more into its native Windows app platform, and do you think open sourcing it will improve things for developers? Let us know in the comments.