Although the Taskbar in Windows 11 has faced backlash from the public for various reasons, Microsoft has been continually experimenting with it. Recent examples include overflow controls and a search widget. Now, it seems like the company might be secretly working on a rounded Taskbar too.
As can be seen above, the rounded Taskbar appeared for a Reddit user u/caipira113 on the latest Windows 11 Dev Channel build 25174. The user alleges that the same thing happened with them on the earlier build 25131. However, the person now has video and photographic proof of it, unlike last time. The Taskbar is floating a bit too as can be seen in the image below:
According to the OP, the rounded Taskbar randomly appeared and persisted even after display driver updates. That said, it disappeared after the user restarted explorer.exe via Command Prompt.
Of course, there is some speculation that this might be doctored evidence. Neowin's co-founder Steven Parker expressed his concerns on the Reddit thread, saying that maybe the tweaking was done with a third-party application like RoundedTB, which was then uninstalled. So, when explorer.exe was restarted any changes made by the application were reverted. However, the Redditor has denied that this is the case and emphasized that they have no reason to deceive people.
Experimental features unexpectedly popping up for select users isn't entirely out of the ordinary. Earlier this year, ad banners started appearing in File Explorer for some people. Microsoft later explained that they were not meant to published externally (...yet?). The same could be the case right now.
It's possible that Microsoft is playing around with the idea of rounded Taskbar to match the design aesthetics of Windows 11, but it may not be ready for public consumption just yet. But again, there's also the slight possibility that this is doctored evidence or a glitch, especially since no one else has seemingly reported this. We'll likely find out the credibility of this report soon, one way or the other.
Update: Microsoft's Brandon LeBlanc has confirmed that this is a bug:
This looks like a bug. There are a few bugs like this that change the UI in various ways. It's not something we're doing any A/B testing on.— Brandon LeBlanc (@brandonleblanc) August 5, 2022