Microsoft plans to start selling its Windows 7 add-on support beginning April 1.

Labeled "Extended Security Updates" (ESU), the post-retirement support will give enterprise customers more time to purge their environments of Windows 7. From Windows 7's Jan. 14, 2020 end of support, ESU will provide security fixes for uncovered or reported vulnerabilities in the OS.

Patches will be issued only for bugs rated "Critical" or "Important" by Microsoft, the top two rankings in a four-step scoring system.

ESU will be dealt out in one-year increments for up to three years and support will be sold on a per-device basis, rather than the per-user approach Microsoft has pushed for Windows 10 licensing. Costs for ESU will start out low - $25 or $50 per year per device - but will double each year, ending at $100 or $200 per device for the third and final year. (The less expensive prices will be for subscribers to Windows 10 Enterprise or Microsoft 365 Enterprise.)

Windows 7 ESU also lets covered PCs run Office 365 ProPlus, the locally-installed applications - Outlook, Word, Excel and the like - bundled with Office 365. Microsoft had previously said that support for Windows 7 running Office 365 ProPlus would dry up when the former reached retirement in January. Another benefit to ESU is that Microsoft will keep patching Internet Explorer 11 (IE11) on eligible Windows 7 machines.

In a March 1 post to a company blog, Bernardo Caldas, general manager of Windows commercial marketing, advised customers interested in ESU to contact their Microsoft account team or reselling partner for purchasing details.