Originally published at endoflife.ai.
Here's a date collision that surprises people: .NET 8 and .NET 9 reach end of support on the same day — November 10, 2026.
The instinctive reaction is "but 8 is the LTS!" — and that's exactly the trap. LTS doesn't mean long, it means longer. The math:
Different tracks, same cliff. Anyone who "played it safe" on the LTS and anyone who rode the STS end up in the identical position this November.
After November 10, Microsoft ships no security patches for either runtime — including for vulnerabilities that get actively exploited later. Your app keeps running; it just stops getting defended. CVEs published against the runtime after that date are permanent for you.
For teams with compliance obligations, "unsupported runtime in production" is an audit finding, not a philosophical debate.
.NET 10 (LTS) shipped November 11, 2025 and is supported to November 14, 2028. For most 8→10 moves the upgrade is mercifully boring — retarget, run the test suite, chase a handful of breaking changes. The teams that get hurt are the ones who discover a transitive dependency pinned to an EOL runtime in December, not the ones who retargeted in September.
Worth separating in your head: .NET Framework 4.8 (the old Windows-only one) is a different animal — it has no fixed end date and lives as long as the Windows version hosting it. Modern .NET (Core lineage) is the one on the November clock. If you're still on Framework, your deadline is your Windows Server's deadline instead.
The November 10 cutoff sits inside a brutal H2 2026 calendar: SharePoint 2016/2019 and SQL Server 2016 already died July 14, OpenSSL 3.0 goes September 7, Python 3.10 on October 31, PostgreSQL 14 on November 12, PHP 8.2 on December 31.
Every date above is verified against vendor lifecycle sources. Full deadline coverage lives at endoflife.ai/eol-watch, you can check any product's status in seconds with the EOL checker, or scan a whole project file with the stack scanner. There's also a free API if you'd rather gate this in CI:
curl https://api.endoflife.ai/v1/status/dotnet/8