Like every version of Windows in the modern era, Windows 10 adheres to a 10-year support lifecycle. That means that most Windows 10 editions -- Home, Pro, Pro Workstation, Enterprise, and Education -- reach their end-of support date on October 14, 2025. (For the nerdy details on how that date is calculated, see "When will Microsoft end support for your version of Windows or Office?")

So, what happens when that day arrives? Nothing. Seriously, absolutely nothing happens on that date. PCs running Windows 10 continue to work just as they always have, and they will do so indefinitely. 

Also: Still have a Windows 10 PC? You have 5 options before support ends next year

From that date forward, however, those PCs will no longer receive security fixes through Windows Update unless their owners pay Microsoft for an Extended Security Updates (ESU) subscription. On Windows 10 PCs without an ESU subscription, however, any security flaws found from that day forward will remain unpatched, making those PCs increasingly vulnerable to online attacks.

There is at least one exception to this cutoff date, which applies to PCs running Windows 10 Enterprise Long Term Servicing editions. In all, Microsoft has released four of these editions. The 2015 Long Term Servicing Branch (LTSB) ends support on October 14, 2025, along with the editions described earlier. The 2016 LTSB release ends support a year later, on October 13, 2026. Beginning in 2019, the name changed to Long Term Servicing Channel (LTSC). For Windows 10 Enterprise LTSC 2019, the end date is January 9, 2029. 

Confusingly, Windows 10 Enterprise LTSC 2021 has only a five-year support lifecycle, which means it ends support on January 12, 2027.

If anyone tells you they know the answer to this one, maybe stop listening to them?

Microsoft can probably make a solid estimate based on its telemetry, but the rest of us are forced to guess based on fragmentary third-party metrics.

Also: How to install Windows 11 the way you want (and sneak by Microsoft's restrictions)

One of the sources I have relied on over the years is the United States Government's Digital Analytics Program (DAP), which has a well-organized repository of information about traffic to official websites run by agencies like the Postal Service, the National Institutes of Health, the National Weather Service, the IRS, and NASA.

When I visited DAP last week, I retrieved data for the 30 days ending August 31, 2024, summarizing more than 1.6 billion visits to those websites from people using computers and mobile devices from all around the world. Here's what the data told me about the visits from PCs and Macs:

That's the real question, isn't it?

Despite predictions of the imminent demise of the PC market, OEMs continue to sell more than 200 million new Windows computers each year. The most optimistic scenario is that every one of those new PCs sold in the next year replaces a Windows 10 device that is then retired, with another 100 million or so older PCs replaced by Chromebooks, iPads, and Macs. Maybe some old PCs are simply put out to pasture and not replaced at all, as consumers decide to use their phones or tablets instead.

Also: The best computers: Comparing laptops, Macs, PCs and more

That best-case scenario still leaves hundreds of millions of people running Windows 10 when the October 2025 end-of-support date rolls around. Who owns those PCs?

• Those who don't qualify for an automatic upgrade. Some people own older hardware that doesn't meet the minimum hardware compatibility standards for Windows 11. Basically, that means any PC that was designed in 2018 or earlier. Note that this category includes many budget PCs that used older designs and unsupported CPUs but were sold as new in 2019 and 2020.

• Corporate PCs that are standardized on Windows 10. A nontrivial number of enterprise IT managers have just finished their Windows 10 migrations in the last year or two and probably aren't anxious to do it again.

• Windows 10 diehards. From my time spent reading support forums, I know there's a large population of longtime Windows users who are unhappy about the changes in Windows 11. Some of them will reluctantly upgrade, but others won't.

That's certainly a possibility, and there's precedent for it in the experience of Windows XP, which ended support in April 2014, more than 12 years after it was first released. Windows XP users even received emergency security updates well after that official end date, to address the WannaCry vulnerability in 2017 and a similar flaw in 2019. Likewise, Microsoft issued emergency security updates for Windows 7 in 2021 after its support had officially ended.

Also: For Windows 11 setup, which user account type should you choose? How to decide

But it's more likely that Microsoft will tell Windows 10 holdouts to pay for Extended Security Updates rather than giving them away for free.

Of course, in both cases, the customers running the soon-to-be-obsolete Windows version had the option to upgrade to a new version. Indeed, that's the recommendation from Microsoft's official Product End of Support page:

Once a product reaches the end of support, or a service retires, there will be no new security updates, non-security updates, or assisted support. Customers are encouraged to migrate to the latest version of the product or service.

For Windows 10, though, that alternative might not be available. Devices that don't meet the hardware compatibility requirements will have no Microsoft-supported migration path to a newer version. As I pointed out the last time I looked at this issue, the owners of those perfectly functional PCs, some only five or six years old, will instead have the following options:

• Install a non-Microsoft operating system. Maybe 2026 will be the year when desktop Linux finally takes hold, although that's unlikely. ChromeOS Flex might be another option, but it has its own hardware compatibility requirements that probably make it unsuitable for older hardware.

• Ignore Microsoft's warnings and upgrade to Windows 11 anyway. There are options to install Windows 11 on "incompatible" hardware, but they require a fair amount of technical experience. People who are clinging to old PCs because they can't afford a new one likely don't have those specialized skills and may not even realize that the option is available. I doubt that many businesses would be willing to risk the support issues that come with that approach.

• Keep running Windows 10 and hope for the best. History suggests that this is the most likely option.

Microsoft and its OEM partners would prefer that the owners of those devices dump them in a landfill and buy a new PC running Windows 11. However, my experience with PC owners, especially older people on a fixed income, is that they will use those devices until they stop working. Those PCs will be sitting ducks for a cyberattack like WannaCry, which was brutally effective against the large population of Windows 7 PCs that were still in use three years after its support ended.

Also: This secret Windows 11 setting lets you kill unresponsive apps much faster

That incident was a PR nightmare for Microsoft, and a repeat would be even more devastating to the company's reputation. That's why Microsoft has offered paid options to extend support for Windows 10 by three years. Customers in enterprise and education deployments are likely to take advantage of those options.

Consumers, though, will apparently be on their own.