You don’t need to install third-party antivirus on Windows 10 or Windows 11. Both come with Windows Security, Microsoft's free built-in protection, and it scores as well as the big paid suites in independent testing. Adding another antivirus app on top will probably slow your PC down without making it any safer.
Why people still install antivirus out of habit
In the early days of Windows, PCs had almost no defenses of their own. Windows had no built-in anti-malware at all until Windows Vista, and that version mostly just blocked spyware.
A fuller antivirus arrived with Windows 8, but few people used Windows 8. Most Windows users didn’t get built-in antivirus until Windows 10 came out in 2015. By then, a decade of habit had set in: install Windows, then install antivirus right away so the PC doesn’t get infected.
That habit no longer matches how Windows works. The protection is now included in the box.
How well Windows Security protects your PC
Independent labs regularly test the major antivirus suites against each other. One measure they use is protection, meaning how well the software actually stops threats. AV-Test runs these tests every few months and rates protection on a scale of 1 to 6, where 6 is best.
Since 2020, Windows Security’s results have been:
- A perfect protection score 33 out of 40 times
- Never below 5.5
- An average score of 5.91
- A 99.74% average detection rate for 0-day threats (new threats with no known fix yet), against an industry average of 99.34% over the same period
It’s free, and it doesn’t bring the extra privacy concerns that come with installing third-party software.
Why third-party antivirus can slow your PC
Any real-time protection costs some performance. Each time a file is scanned or an app is checked at launch, your PC has to spend time analyzing it, and it may upload something to the cloud for further analysis. Ideally, that delay is small enough that you never notice it.
For a long time, many third-party suites were heavy enough that you did notice. They could cause visible pauses when you opened a file or make apps launch much more slowly. This matters most on older or low-power devices.
Windows Security does well here. In 40 benchmarks it got a perfect performance score 31 times, with an average score of 5.83. A bug in 2022 hurt its performance scores noticeably, and that bug has since been fixed.
When it comes to browsing speed, opening files and running apps, Windows Security keeps up with the best third-party options.
Why third-party antivirus is so noisy
Most third-party suites keep interrupting you even when they’re working fine. You get update reminders, discount ads, push notifications about new features and more.
A good antivirus should stay out of sight and only alert you when something urgent happens, such as finding malware. Windows Security works this way. Its notifications usually come when it flags a download as potentially harmful.
The one place Windows Security is slower: installing apps
Windows Security is noticeably slower than competitors when you install a new program. It scans every file a new program writes to your drive.
Many third-party tools use faster shortcuts instead, such as reputation checks or allowlists (lists of software already known to be safe). Those methods are generally safe but less thorough.
For most people the trade-off is worth it, because clever malware exists and thorough scanning catches more. You probably don’t install new software often. Even someone who tests new apps all the time might install two on a workday and one on a weekend day, so slower installs aren’t likely to affect your day-to-day use much.
What third-party antivirus companies offer now
Third-party antivirus companies still exist, but most of the free options are now owned by one company. These products now compete less on virus protection and more on extras like identity protection, phishing protection and dark-web monitoring.
If you want those extras, a third-party suite may still appeal to you. For antivirus protection on its own, Windows Security is enough.
Frequently asked questions
Does Windows 11 have built-in antivirus?
Yes. Windows 11 and Windows 10 both include Windows Security, which provides antivirus protection without installing anything else.
Is Windows Security as good as paid antivirus?
In AV-Test results since 2020, it averaged 5.91 out of 6 for protection and detected 99.74% of 0-day threats, above the industry average of 99.34%.
Why is installing programs slow with Windows Security?
It scans every file a new program writes to your drive. Many third-party tools use faster but less thorough checks, such as reputation or allowlists.
Does Windows Security slow down my PC?
Not much in normal use. It averaged 5.83 out of 6 for performance across 40 benchmarks, and the 2022 bug that hurt its scores has been fixed.
