Developers use it to test app compatibility with new icons and the updated Windows Terminal default setting.
Despite being an Insider Preview, Build 21390 introduced several notable features:
: It is often cited as the last viable Windows 10 build for ARM64 virtualization (e.g., on Apple Silicon) before Microsoft shifted focus to Windows 11. ISO Availability & Status Announcing Windows 10 Insider Preview Build 21390
Although this build focused heavily on testing the "servicing pipeline" through multiple cumulative updates, it introduced several notable visual and functional tweaks: windows 10 insider preview build 21390 x86 x64 iso incl
: Fixed blurry text in the "news and interests" taskbar widget for specific resolutions.
The leak of Build 21390 caused a significant stir within the Windows Insider community. Some users were thrilled to have access to the latest build, while others expressed concern about the potential security risks.
Since Microsoft's official download page only offers the most recent ISO builds, getting older Insider builds like 21390 requires a few more steps. Here's how you can get it: Developers use it to test app compatibility with
Windows 10 Insider Preview Build 21390 was a minor, yet important, stepping stone in the journey toward a more modern Windows experience. With its focus on updating legacy icons and fixing underlying system issues, it provided a glimpse into the design philosophy that would soon define the next generation of Windows. For those who used the ISO to clean-install the system, it offered a glimpse into a faster, cleaner interface. If you are currently on an older build, I can help you:
Addressed an issue impacting Start Menu reliability in previous flights.
Released on May 26, 2021, Windows 10 Insider Preview Build 21390 marked a significant point in the development cycle, bringing visual refinements and technical improvements to the Dev Channel. This build was particularly notable for updating the look of legacy tools and offering enhanced terminal customization. The leak of Build 21390 caused a significant
Windows 10 Insider Preview Build 21390 was a significant release for the Dev Channel in May 2021. Often referred to as the "Cobalt" release (co_release), this build is highly regarded among enthusiasts as the "final" true Windows 10 Insider build before Microsoft shifted focus to Windows 11.
Windows 10 Insider Preview Build 21390 is best suited for deployment in or on secondary testing hardware. Because preview builds are unstable by design, installing this build on a primary workstation or production machine is not advised. Always back up critical data before performing any OS installation or upgrade.
| Feature | x86 (32-bit) | x64 (64-bit) | | :--- | :--- | :--- | | | 4 GB (3.2 GB usable) | 2 TB (theoretically 4 PB via PAE) | | System Type | Older tablets (Intel Atom), legacy POS systems | Modern desktops, laptops, workstations | | Performance | Lower overhead, but memory-bound | Full performance, supports >4GB RAM | | Software Compatibility | Runs 16-bit apps (via NTVDM) | Runs 32-bit & 64-bit apps, not 16-bit | | Recommended Use | Virtual machines (low RAM), vintage netbooks | Daily driving, gaming, development |
Before you download Build 21390, keep in mind that this is a pre-release version of Windows 10, and it may contain bugs and issues that can affect your user experience. Make sure to back up your important files and data before installing this build.
Build 21390 is recognized as a late-stage Windows 10 development build that acted as a bridge to Windows 11. It featured early, internal implementations of visual changes that would define the new OS before it was officially announced.