Can I use the same Microsoft Office Home & Student 2021 license that I received with my Windows laptop to install and activate Office on my MacBook?

Office keys are platform specific so, no, in general it won't work. Your license key for Windows won't work on Mac. If you got the software as part of an OEM bundle then this is more likely.

But you said you log into your MS account on the Mac and you see the option of downloading Office. You're doing that through a website so all it likely knows is that you have an Office license and not, at this point, that you're on a Mac. If it knows you have an Office license just based upon your MS account then it sounds like you might have a digital license. In that case you should be able to install it on the Mac as well. If it simply shows you a product key then you have a Windows-only license.

Of course this is easy to confirm, just select the option to install the Mac version. If it doesn't give you this option then it won't work. In my case I don't have an option to install for Mac. If you do have the option to install then install it. After installation it should try to authenticate. If your license is good then it will work. If it fails then you'll need to get a license. Note that an MS 365 Family Subscription is generally cheaper than buying a license for the product. So if you find you need to get a license then you might look into a subscription first.

Dear @Abhiram Krishna T

Thank you so much for contacting Microsoft Q&A Forum. 

Based on your description, I would like to provide some information for you about your concern, and you can check on your side to see if you use it on your Mac. 

Normally, Office Home & Student 2021 licenses can be transferred to another device if it's a retail license. Microsoft allows transferring Office 2021 to another computer owned by the same person, but only once every 90 days, unless the transfer is due to hardware failure. 

Reference: Transfer your Office license to another device or another person - Microsoft Support 

However, OEM licenses (often bundled with new PCs) are tied to the original device and cannot be transferred. You can consult in this case: OEM Office 2021 - Microsoft Q&A 

So, if you want to check the license is OEM or retail, you can go to the Office app menu on your Mac (eg. Word > choose About Word). It will show the license type and Mac versions typically only support retail or volume licenses, not OEM. 

Reference: About Office: What version of Office am I using? - Microsoft Support 

After checking, if it's a retail license, you can do these steps: 

• Sign in to your Microsoft account at account.microsoft.com. 
• Go to Services & subscriptions. 
• Find your Office Home & Student 2021 license. 
• Click Install Office. 
• Download and install Office on the MacBook. 
• Activate using the same Microsoft account. 

I hope this information can help you to clarify your concern. 

Wish you a pleasant day! 

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