An Office product key<\/strong>, also called an activation key or license key, is a code of 25 characters<\/strong> split into five groups of five, in the form XXXXX-XXXXX-XXXXX-XXXXX-XXXXX. It does not contain the software: the installation files are downloaded free of charge from Microsoft. The key represents your right to use the suite. When you enter it, Office contacts Microsoft’s activation servers, which check that the key exists, matches the installed product and has not already been used up, then activate your copy.<\/p>\n Without a valid key, Office switches to reduced functionality: a permanent warning banner, editing and saving blocked after a grace period, documents available read-only. With a valid key, the suite is activated for good if it is a perpetual license, or for the length of the subscription with Microsoft 365. If you see the red “Unlicensed Product” banner, our guide to the Office unlicensed product error<\/a> explains how to fix it.<\/p>\n A key unlocks one product only: an Office 2021 key will never activate an Office 2019 installation, and a Pro Plus key does not unlock a Home edition. This is the first cause of the “product key not valid” message. Always check the edition you have downloaded before typing your 25 characters. If Office says the key is already in use, see our guide to error 25004<\/a>.<\/p>\n The keys below all activate a perpetual license on one Windows PC. The difference lies in the version, the apps and, above all, how long Microsoft keeps publishing security updates.<\/p>\nEach key matches one specific version<\/h3>\n
Which Office product key do you need?<\/h2>\n