Microsoft will use on-device data and other factors to determine which devices will get the offer to upgrade first, the company said in a blog post Tuesday.
The upgrade will be available on eligible Windows 10 PCs and PCs that come pre-loaded with Windows 11. The company expects all eligible devices to be offered the free upgrade by mid-2022.
The new operating system will be "the best Windows ever for gaming."
Windows 11 comes six years after Microsoft released Windows 10, marking the longest stretch the company has had between new Windows launches, according to CNBC.
Microsoft shares were down 0.02% to $303.54 on Tuesday at last check.
Revenue from Windows accounted for $6.6 billion in the second quarter, about 14% of the company's total revenue.
Microsoft's stock hit an all time high above $305.30 earlier this month as the stock has risen nearly 40% year to date while it chases Apple (AAPL) - Get Free Report to be the world's most valuable tech company.
Microsoft topped Wall Street forecasts in its record fourth-quarter earnings in July thanks in part to its market-leading cloud computing division.
Microsoft Azure saw a 51% jump in fourth-quarter revenues as the shift towards working from home helped the division achieve new heights.