Microsoft’s Fixed Lifecycle Policy is a support model that gives a product a defined service window, usually split into mainstream support and extended support. During mainstream support, customers get the widest range of fixes and servicing options. In extended support, security updates may continue, but non-security changes, feature work, and some support options are reduced or removed.
In cyber security, this matters because attackers often target systems that are still running but no longer have the same vendor flexibility. A product under a fixed lifecycle can remain secure if it is patched and managed carefully, but teams must track support dates, plan upgrades, and confirm edition-specific servicing rules. Defenders use lifecycle management to reduce risk, avoid surprise end-of-support gaps, and keep critical servers on a known patch path.