How to Activate Microsoft Office with a Product Key (Step by Step)

To activate Microsoft Office with a product key, you redeem the key on your Microsoft account, install Office and sign in. The whole process takes about 10 to 15 minutes. This guide shows each step for Office 2021 and Office 2024 on Windows, and explains how to fix the most common activation problems.

Last updated: 21 September 2026. Steps follow Microsoft support pages: Redeem a product key or activate Office and Where to enter your Office product key.

Before you start

• A Windows 10 or Windows 11 PC. Windows keys do not work on a Mac.
• Your 25-character product key from your order email.
• A Microsoft account (you can create a free one during setup).
• An internet connection, at least 4 GB of RAM and 4 GB of free disk space.
• Not sure which version to buy? Read our guide on Office 2021 end of support.

Step 1: Redeem your product key

1. Go to setup.office.com in your browser.
2. Sign in with your Microsoft account, or create a new one. Use an account you will keep, because the license is linked to it.
3. Enter your 25-character product key. You can leave out the hyphens.
4. Select your country or region and your language.
5. Confirm the product name and select Redeem.

A product key can only be redeemed once.

Step 2: Download and install Office

1. Go to account.microsoft.com/services and sign in with the same account.
2. Find your Office product and select Install.
3. Choose the options you want, such as 64-bit and your language, then select Install again.
4. Run the installer and wait until it finishes.

Prefer a walkthrough of the download step specifically? See our Office 2024 download guide.

Step 3: Activate Microsoft Office

Open Word or Excel and sign in with the same Microsoft account. Office activates automatically. To check, click File, then Account. You should see Product Activated.

Alternative: enter the key inside an Office app

For Office Professional Plus, Visio Professional and Project Professional, Microsoft also describes another method. Open an Office app such as Word. In the Sign in to set up Office window, select I do not want to sign in or create an account, then enter your product key without hyphens. If your seller sent different instructions, follow those.

Common activation problems and fixes

• This product key has already been used: a key can only be redeemed once. If you redeemed it with your own account, sign in at account.microsoft.com/services and install Office from there. If you did not, contact your seller.
• Invalid product key: retype the key carefully and check the letters and numbers that look alike, such as 0 and O. Make sure the key matches your version. An Office 2021 key does not activate Office 2024.
• Wrong account: sign in to Office with the same Microsoft account you used to redeem the key.
• Older Office version installed: uninstall it in Windows Settings under Apps, restart, then install again.
• Not activating: check that your internet connection works and that your PC date and time are correct. Then close every Office app, open one again and sign in.

Running into a Windows (not Office) activation error code instead? See our guide on Windows activation errors and fixes.

Reinstalling Office later

Once your key has been redeemed, you usually do not need it again. Sign in at account.microsoft.com/services and select Install. See also Microsoft: Get help with setup.office.com.

Need a license? Browse Microsoft Office licenses or see Office 2024 Professional Plus.