How to Activate Microsoft Office (2019, 2021 and 2024) on Windows

Office activation has one step people miss: the key goes into the Office application itself, not into Windows. This guide covers Office Professional Plus and Office Standard 2019, 2021 and 2024 on Windows.

In short

• Install the correct Office edition first. Remove any older Office or Microsoft 365 installation before you do.
• Open Word or Excel, then File → Account → Change Product Key.
• Paste the 25-character key and confirm. If it is refused, you can use the Microsoft Activation Portal instead.

Step 1: install Office first

A product key does not download Office — it unlocks an installation that is already on the PC. If Office is not installed yet, install it before you go any further.

If you still need the installer, here is where to get it:

• Office 2021 Professional Plus — download (about 4.4 GB)
• Office 2019 Professional Plus — download (about 4.1 GB)

Both are .img disc images. On Windows 10 and 11, double-click the file — it mounts as a drive — then run setup.exe inside it.

Office 2024 Professional Plus comes as an installer rather than a disc image:

• Office 2024 Professional Plus — download the installer (3.5 MB)

Run it and leave it alone until it finishes. The file itself is small because Office is downloaded from Microsoft while it runs, so give it time on a slow connection. When it is done, activate Office with your key using the steps below.

If you would rather install it yourself — on several machines, or with your own settings — Microsoft documents the process in its deployment guide for Office 2024.

Install only one Office version. A trial copy of Microsoft 365 that shipped with the PC, or an older Office left in place, is the single most common reason a valid key is refused. Remove any other Office version through Settings → Apps → Installed apps first, then restart.

Step 2: enter your product key

• Open any Office application — Word or Excel is easiest.
• If an activation wizard appears on launch, enter your 25-character key there and follow it through.
• If no wizard appears, go to File → Account.
• Click Change Product Key under the product information.
• Enter the key and confirm.

Office contacts Microsoft, activates, and asks you to restart the application. That restart matters — the licence state only refreshes when Office starts fresh.

Step 3: confirm it worked

Go back to File → Account. Under Product Information you should see your Office edition and the words Product Activated. If a yellow or red banner still runs across the top of the document, activation has not completed.

Visio or Project?

They are separate products with their own keys, and installing them next to an existing Office has one rule that decides whether it works at all. See our Visio and Project activation guide.

Using a Mac?

Office for Mac is activated a different way — the key is redeemed in a Microsoft account rather than typed into Word, and the licence then follows that account rather than the machine. It has its own guide: how to activate Office for Mac.

Common problems

• "The product key you entered cannot be used to activate this product." The key belongs to a different Office edition or version — an Office 2021 key will not activate an Office 2024 installation, and a Professional Plus key will not activate Home & Business.
• Office keeps asking you to sign in. That is Microsoft 365 asking, not your Office installation. A trial of 365 is still present — uninstall it and restart.
• The banner says the licence is not genuine. Close every Office application, reopen one, and check File → Account again. Office often reports the previous state until it restarts.

Anything else — take the exact wording of the message to our Office activation troubleshooting guide, or send it to us with your order number.