Attackers create fake KMS servers (or local emulators) that trick your Office installation into thinking it is inside a legitimate corporate network.
This is the most common "product key free" method found on YouTube and forums. KMS is a legitimate Microsoft technology used by large corporations to activate hundreds of PCs on a local network without entering keys on each machine. how to activate microsoft office without product key
Microsoft is aware of all these methods but rarely sues individual users. Instead, they use "nag screens" (red banners in Office) and feature degradation. Since 2023, unactivated Office 2021/365 will eventually enter "reduced functionality mode" (view only, cannot edit) after 30 days, rendering most bypass methods obsolete. The only truly sustainable keyless solution is switching to the free web apps or an open-source alternative like LibreOffice. Attackers create fake KMS servers (or local emulators)