Once again, Microsoft released this week's Windows 10 Insider Preview build on a Friday. Build 21387 is available in the Dev channel. The most notable thing is that this is the first build to ship without Internet Explorer enabled.

Microsoft recently announced dates for when it's killing off Internet Explorer in Windows 10. However, it's not actually removing the legacy browser from the OS. Indeed, today's build does ship with IE11; you just can't use it.

Instead, businesses that rely on Internet Explorer are going to be using IE mode in the Edge browser. Still, IE mode needs Internet Explorer to exist for the engine.

As for what else is new in Windows 10 Insider Preview build 21387, there really isn't much, or anything else of note. Microsoft said that it's turning off the Eco mode in Task Manager to improve the experience, but that's it. The rest is a bunch of fixes and known issues.

This is a preview from the Dev channel, which means it's not officially tied to a release of Windows 10. The build is from the co_release branch, which one would think ties it to the 21H2 'Cobalt' release, but apparently not. Either way, most of the new features that we have will get split into a proper Windows 10 21H2 release.  That should show up in the Beta channel. While 21H1 is released, leaving the Beta channel open for a new release, it might be some time before 21H2 goes to Beta.

Windows 10 RTMs in June and December, so it's more likely that we should see Windows 10 version 21H2 in the Beta channel in July. That way, it can be serviced for a few months before it's released in October. There's also more coming in Windows 10 version 21H2, such as the Sun Valley UI overhaul that's on the way. We should hear more about that at a Windows event in June.

For now, just know that when you install this build of Windows 10, Internet Explorer will be disabled and you'll have to use Edge. But if you're still on IE, it's unclear what you're doing on the cutting edge of Windows previews.