Office 2021 Professional Plus Download & Installation Guide

Last reviewed 25 September 2026 by Jay, Technical Support Advisor at Nerdused. Meet the support team

This guide is for Office Professional Plus 2021 on Windows 10 or 11: where to download the installer, how to check it is the file we published, how to install it, and how to activate it with the key from your order email. It takes about 15 minutes plus the download. Go straight to the Office 2021 Professional Plus download links (64-bit and 32-bit, seven languages).

Microsoft support for Office 2021 ends on 13 October 2026. It installs and activates normally and keeps working after that date, but it stops receiving security updates. If you want a version with years of support left, Office Professional Plus 2024 is supported until 9 October 2029.

What you are installing

Edition	Microsoft Office Professional Plus 2021 (volume-licence release, Office LTSC 2021 build)
Apps included	Word, Excel, PowerPoint, Outlook, OneNote, Publisher, Access, Skype for Business. Access is only in the Professional Plus edition. Publisher is in Professional Plus and Standard, but not in Home & Business.
New since Office 2019	XLOOKUP, dynamic arrays, LET and XMATCH in Excel; dark mode across the apps; Line Focus in Word; recording with ink in PowerPoint; better performance opening large files. Office 2021 is the last perpetual version that includes Publisher.
Not included	Teams, OneDrive storage, Copilot and the cloud-only features of Microsoft 365. Co-authoring works only for files saved to OneDrive or SharePoint.
Runs on	Windows 10 or Windows 11 (and Windows Server 2019 or later). Office 2021 does not install on Windows 7 or 8.1.
Minimum hardware	1.6 GHz dual-core processor, 4 GB RAM (64-bit), 4 GB free disk space, 1280 × 768 display, internet connection for download and activation
Version / channel	Office 2021 Version 2108, Perpetual Volume Licence 2021 channel. The installer downloads the current 2021 build from Microsoft's servers, so you get the latest security update on day one
Licence	This is a volume-licence build (the installer's configuration uses Microsoft's PerpetualVL2021 channel with product ID ProPlus2021Volume), so it activates with a Multiple Activation Key (MAK) rather than a retail key. Enter the key in any Office app under File → Account → Activate Product, or from an administrator Command Prompt: cd "C:\Program Files\Microsoft Office\Office16" (32-bit Office on 64-bit Windows: cd "C:\Program Files (x86)\Microsoft Office\Office16") then cscript ospp.vbs /inpkey:YOUR-KEY and cscript ospp.vbs /act. cscript ospp.vbs /dstatus shows the activation state.
Microsoft support	Ends 13 October 2026. Security updates stop on that date; the software keeps working. Office Professional Plus 2024 is supported until 9 October 2029
Installer	3.1 MB self-extracting package containing Microsoft's Office Deployment Tool (Bootstrapper 16.0.14326.20384, signed by Microsoft Corporation) and a configuration file; the Office files themselves (about 3 GB) download from Microsoft during Step 2

Download Office Professional Plus 2021

Pick your language and choose 64-bit unless you know you need 32-bit (32-bit is only for old add-ins that require it; Windows 11 is always 64-bit).

The key you have bought is a prepaid activation code for this installer. It does not activate an Office that came pre-installed on a new PC or a Microsoft 365 trial; install from the download above, then enter the key.

Verify your download

Every installer is a self-extracting package that contains Microsoft's Office Deployment Tool (setup.exe, signed by Microsoft Corporation) and a small configuration.xml that tells it which edition and language to fetch. Before you run it, you can check that the file you downloaded is the one we published: open PowerShell in your Downloads folder and run certutil -hashfile FILENAME.exe SHA256. The result must match the checksum below exactly.

File sizes and SHA-256 checksums (click to expand)

File	Size	SHA-256
Office_2021_EN_64Bits.exe	3,115,784 bytes	c8d82c2a5c68a5214e5d39351f21e2ff5b9d67bf2ff2da7756d5772319af8a83
setup.exe inside the package (Office Deployment Tool 16.0.14326.20384)	7,423,816 bytes	aae9c94bc546d208868bc04a823ad6a716b1b4d3ad7010263b0690082e3b8da8

Checksums for the other language packages are being added; until then, use the digital-signature check above for those files.

Before you start

• Check Windows: Office 2021 needs Windows 10 or 11 and refuses to install on Windows 7 or 8.1.
• Have your Professional Plus 2021 key from the order email ready (25 characters, in five groups of five).
• Remove any other Office or Microsoft 365 install first (Step 1). Click-to-Run will not install 2021 alongside a different edition.
• Allow about 3 GB of download and 10–20 minutes. Keep the PC awake until the installer says it is done.

How to Install Microsoft Office 2021 Professional Plus

Three steps: remove any existing Office, run the installer as administrator, then enter your key. Most installs finish in 10–20 minutes.

Step 1: Uninstall Existing Microsoft Office (Required)

Before installing Office Professional Plus 2021, remove any previous versions to avoid conflicts.

1. Open the “Control Panel”.
2. Select “Programs and Features”.
3. Find Microsoft Office in the list, right-click, and select “Uninstall”.
4. Follow the uninstallation wizard instructions.

Note: The process may take several minutes, depending on your computer’s configuration. If the uninstall fails or Office still shows in the list afterwards, run Microsoft's Office uninstall support tool.

Important: Restart your computer after uninstalling.

Step 2: Install Microsoft Office 2021 Professional Plus

After downloading the Office installer:

1. Go to your Downloads folder

2. Locate the installer file (Office_2021_EN_64Bits.exe)

3. Right-click and select Run as administrator

4. Follow the on-screen instructions

5. Select the “Install” button. This extracts the Office Deployment Tool and starts the download from Microsoft; the progress window closes on its own when the installation is complete.

Step 3: Activate Microsoft Office

Method 1: Online Activation

1. Open any Office app. You will be prompted to enter the activation key the first time you launch an application from the suite.

If the prompt did not appear, open Word, go to File → Account → Activate Product, and enter the key there. Until a key is entered, Office runs as an unlicensed copy and the apps switch to read-only after the grace period.

Method 2: Phone Activation (use this if online activation is blocked or returns an error)

1. Open any Office app

2. Go to File → Account

3. Click Activate Product

4. Select Enter Product Key

5. Enter your product key

6. Choose Phone Activation

7. Take note of the Installation ID (or run cscript ospp.vbs /dinstid in the Office16 folder to display it; after getting the Confirmation ID, apply it with cscript ospp.vbs /actcid:CONFIRMATION-ID then cscript ospp.vbs /act)

Complete Activation via Microsoft Portal

1. Visit https://visualsupport.microsoft.com/

2. Click Let’s Get Started

3. Sign in with Microsoft Account

4. Select Activate a Microsoft Product

5. Choose Microsoft Office and Windows OS

6. Enter Installation ID

7. Obtain Confirmation ID

8. Enter Confirmation ID in Office activation window

Your Microsoft Office 2021 Professional Plus should now be installed and activated. File → Account should read “Product Activated”.

Common errors and the fix for each

• 0xC004F074 (“The Key Management Server could not be contacted”) — The volume build is still using the generic KMS key the installer adds, so it looks for a company KMS server that does not exist. Enter your MAK with cscript ospp.vbs /inpkey:YOUR-KEY then cscript ospp.vbs /act from an administrator Command Prompt in the Office16 folder, or use File → Account → Activate Product.
• 0x80070005 (“Access denied”) during activation — The command or app was not run with administrator rights. Close it, right-click Command Prompt or Word and choose Run as administrator, then activate again. “We couldn't contact the server” — A firewall, VPN or work network blocked online activation. Turn the VPN off and try again, or use Method 2 (phone activation), which does not need the activation servers to be reachable from the PC.
• “Unlicensed Product” banner across the top of Word or Excel — Office installed but was never activated, or the grace period ran out. Go to File → Account → Activate Product and enter your key. If the key is rejected, send us the exact message shown.
• “We're sorry, Office can't install because another version of Office is already installed” — Click-to-Run refuses to install next to an existing Office or Microsoft 365 install. Remove the old version (Step 1 above, or the uninstall support tool), restart, and try again.
• The installer opens and closes with nothing installed — Usually the download was interrupted. Check the file size and SHA-256 against the table above, re-download if it differs, and run it as administrator with antivirus real-time scanning paused for the install.
• “This product is not supported on this operating system” on Windows 7 or 8.1 — Office 2021 requires Windows 10 or later; there is no workaround. Upgrade Windows first (see our Windows 11 upgrade guide).

Questions we get about this edition

Is Office 2021 still worth buying with support ending on 13 October 2026?

For a PC that mostly works offline or with files you trust, yes: it is the cheapest way to get Publisher and Access with a one-time payment, and it keeps working after the date. For a machine that opens email attachments and downloads all day, Office Professional Plus 2024 is supported for three more years and costs little more. Our Office 2024 editions guide compares them.

Does the 2021 key work on the 2019 or 2024 installer?

No. Keys are edition-specific: a ProPlus2021 key only activates the 2021 build. Use the download links on this page.

Can I install it on more than one PC?

The option you bought decides that: a 1-device key activates one PC, a 3-device key three. Reinstalling on the same PC later is fine; activate again with the same key.

Why does the download come from Microsoft rather than from you?

The 3 MB package only contains Microsoft's Office Deployment Tool and a configuration file. The 3 GB of Office itself is fetched from Microsoft's own content network, which is why the software is always the genuine, current build and why you need an internet connection during Step 2.

Does it include Teams or OneDrive?

No. Those are Microsoft 365 services. You can install the free Teams app and use a free OneDrive account alongside Office 2021, but they are not part of the licence.