Windows 10 is the big one that’s already obsolete in 2026, and Microsoft’s free Extended Security Updates only run until October 13, 2026. Another Windows version that’s being phased out in 2026 is Windows 11 SE, whose support ends in October 2026.

What this means

  • Windows 10 : support ended on October 14, 2025, so it is the main version people are now treating as obsolete in 2026.
  • Windows 11 SE : Microsoft says support ends in October 2026.
  • Windows 11 24H2 : another version scheduled to lose support in 2026, with reporting pointing to October 13, 2026.

Practical takeaway

If you’re asking which version is “about to go obsolete” in the most common sense, the answer is Windows 10. If you mean versions still on a countdown in 2026, Windows 11 SE and Windows 11 24H2 are also on the list.

Timing note

Microsoft’s 2026 support deadlines mean some PCs will still run these versions for a while, but they’ll stop getting security fixes once support ends. That is usually the point when a version is considered obsolete for everyday use.

TL;DR: Windows 10 is the main obsolete Windows version in 2026, with Windows 11 SE and Windows 11 24H2 also reaching end-of-support this year.