A product key in Microsoft Office is a 25-character code used to activate the software and verify that it has not been used on more devices than the license allows.
For most tasks, such as activating Microsoft 365 and reinstalling Microsoft 365, your Microsoft account takes the place of your product key.
The product key is typically found on a product key card and will always be shown in the format XXXXX-XXXXX-XXXXX-XXXXX-XXXXX.
If you purchased Office Home & Business, Office Professional, or individual Office apps, you can view your product key online on the Services & Subscriptions page through your Microsoft account.
If you are prompted for a product key when installing Office through your employer's Microsoft Workplace Discount Program benefit, you will need your product key to install Office on a PC.
