Windows 11 build 21343

Windows 11 build 21343 is an interim build of Windows 11. Video footage can be found within the portfolio of Albert Yih, who represented their role as the product motion design lead on Windows at Microsoft during development. It is notably one of the earliest known builds of Windows 11 to feature the new user interface changes that would be later found in the retail release, and is overall similar to what is found in builds 21996 and 22000.1.

This build is one out of three known builds to be compiled from a branch with the  prefix, the other two being builds 21327 and 21380. The prefix stands for Firesteel, the codename for an internal Microsoft tool related to Windows 11 development.

New features and changes
This build contains a significant number of new and updated features in relation to the user experience. The Aero visual style has been updated to feature new neumorphic controls and widgets. The new design makes large use of elements such as rounded corners, shadows, as well as blue accents. Window frames have also been updated to use rounded corners.

User interface
An early iteration of the new taskbar, similar to the one featured in Windows 10X, has been introduced. Unlike previous versions of Windows, the Start button and application buttons are centered by default, rather than aligned to the left. The taskbar at the time of the build's compilation appears to be similar to the later Taskbar design observed within build 21380, featuring theme-aware grayscale buttons (later observed in build 21354, removed in late development builds) in place of the later colorful icons and a different Task View icon design. Taskbar application icons now include responsive animations based on the current state of a window, for example whether a window is focused or not. In addition, application badges have also been introduced, allowing for applications to report their current status (such as the total number of notifications or profile states) in real-time.

Compared to later builds, the older Action Center and File Explorer ribbon designs are still present in this build and would persist up through build 22000.9, where they would be later replaced with an overhauled Control Center and a simplified ribbon in build 22000.51.

The News and interests flyout has been disabled in favor of the then-new Widgets feature, as evidenced by the presence of its icon within the taskbar. Based on the contents of a partially-visible internal Microsoft email observed within the video, it is likely that the overall Widgets UI design is mostly similar to what is found in build 21996.

Iconography improvements
Many icons in  and   have been updated to follow the Fluent Design system. As a result, those used in user folders, drives, ribbon items, and other areas in File Explorer, including Run, have been refreshed. These design updates would be later pushed out to Insiders in the decoy branch compile of Cobalt build 21343.