Windows 10 build 21390 in the Dev channel has more new icons

Windows 10 build 21390 in the Dev channel has more new icons

After a couple weeks of new Windows 10 Insider Preview builds on Fridays, the team seems to be back on schedule with its usual Wednesday build. Windows 10 build 21390 is now available for Insiders on the Dev channel.

What’s new in Windows 10 build 21390

You shouldn’t be surprised to hear that there’s very little that’s new. In fact, it’s really just new icons for the Task Manager and for MSI installers, and that wasn’t even deemed important enough for Microsoft to include pictures of the icons in the blog post. The other thing listed as a new feature is that Windows Terminal Preview can be set as your default terminal emulator, but that’s not a feature of the build. That’s an app update.


Naturally, there’s also a long list of fixes, such as fixing some scaling issues with news and interests. There are some minor known issues as well.

So what’s really going on?

But let’s talk about what’s really going on here. If you’re on the Dev channel, Microsoft promised that you’d be in a perpetual state of prerelease. You enrolled because you want all the new features. And right now, you’re not getting any.

This build is from the co_release (co for Cobalt) branch, not rs_prerelease. This is something that Microsoft does every six months when a feature update is about to RTM. To be clear, Windows 10 RTMs in June and December. After that, it heads out to the Beta channel of the Insider Program and receives cumulative updates for a few months before being released to everyone.

This process is never really as straightforward as it seems. Windows 10 versions 20H2 and 21H1 both had mn_release (mn for Manganese) and fe_release (fe for Iron) branches, but those didn’t actually turn into feature updates. Those updates were just enablement packages that lit up some features that were already hidden in the OS. Creating release branches in the Dev channel was really just Microsoft going through the motions.

Wait, but I thought Sun Valley was coming this fall

This particular release branch is also a bit strange, because Microsoft actually does have new features coming. The codename is called Sun Valley, and it’s a major overhaul of the operating system. We’ve been seeing some hints of it in rs_prerelease builds up until this point, but not the big changes we’re expecting. It’s also what Microsoft is promising to deliver instead of Windows 10X.

Microsoft just doesn’t want to show it to you yet. The Redmond firm is planning an event that’s going to take place in early June. Things should move pretty quickly from there, because Sun Valley is pretty much done.

You’re going to see Microsoft show off everything at an event, and then it will probably show up in a Windows Insider Preview later on that week. From there, it will still RTM by the end of June and then ship fall.

In other words, the lull in new features from Windows 10 builds in the Dev channel is temporary. Don’t be surprised if next week’s build doesn’t have anything exciting either, but there’s definitely more to come and there’s a lot of it.

About author

Rich Woods
Rich Woods

Managing Editor for XDA Computing. I've been covering tech from smartphones to PCs since 2013. If you see me at a trade show, come say hi and let me ask you weird questions about why you use the tech you use.

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