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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchFor many Windows 11 home users, Microsoft Defender is a credible built-in antivirus baseline; a third-party suite is optional, not an automatic upgrade. Consider another product when its additional features or tested performance and usability match a specific need. In AV-TEST’s August 2026 comparison, Defender earned full protection and usability scores, while several third-party products did too.
What does Microsoft Defender include?
Microsoft Defender Antivirus is included with Windows 11. Microsoft says it continually monitors for malware and other threats and downloads updates automatically. Its protection includes real-time, behavior-based, heuristic, and cloud-delivered approaches. Microsoft’s Defender Antivirus documentation describes these capabilities.
Defender Antivirus is one component of Windows security, not the name for every security feature in Windows. For example, Microsoft describes Network protection as helping protect against phishing sites, malware, tech-support scams, and malicious downloads across third-party browsers and processes. Microsoft’s Windows security overview discusses this broader protection.
Scans and real-time protection
Windows Security offers quick, full, custom, and offline scans. An offline scan restarts the PC into the Windows Recovery Environment and can scan without an internet connection. Microsoft warns that if you disable real-time protection, files opened or downloaded while it is off will not be scanned until a later scan. Microsoft’s Windows Security guidance explains the scan options and caveat.
#1 Best Overall
How did Defender compare with third-party products?
AV-TEST evaluated 15 home-user security products using default settings in July and August 2026. The lab used current publicly available versions, real-world threat scenarios, and available product layers. It awarded up to six points each for protection, performance, and usability, for a maximum of 18. These scores apply to the named versions and test period; they do not guarantee the same results on every PC or in future releases. See AV-TEST’s August 2026 Windows 11 comparison.
| Product tested | Protection | Performance | Usability | Overall |
|---|---|---|---|---|
| Microsoft Defender Antivirus (Consumer) 4.18 | 6/6 | 5.5/6 | 6/6 | 17.5/18 |
| Bitdefender Total Security 27.0 | 6/6 | 6/6 | 6/6 | 18/18 |
| ESET Security Ultimate 19.1 & 19.2 | 6/6 | 6/6 | 6/6 | 18/18 |
| Norton 360 26.6 & 26.7 | 6/6 | 6/6 | 6/6 | 18/18 |
In a separate May–June 2026 AV-TEST review of Defender Antivirus Consumer 4.18 on Windows 11 Professional 64-bit, it scored 6/6 for protection, 5.5/6 for performance, and 6/6 for usability. Its zero-day real-world threat results were 100% in each month, as were its results against the recent widespread-malware reference set. Those are results for the specific tests and period, not a promise of perfect detection against every threat. See AV-TEST’s detailed Defender review.
Rank #2
Why performance scores can vary
Antivirus performance depends on the test setup and activities measured. AV-Comparatives’ April 2026 low-end performance test used an up-to-date Windows 11 64-bit system and measured activities such as copying files, installing and launching applications, downloading files, and browsing. The report says its results apply to the named product versions and 64-bit systems; it does not establish a numeric result for a product not specifically reported here. Read AV-Comparatives’ April 2026 performance report.
Should you install a third-party antivirus?
Start with what you actually need beyond the antivirus protection already included. A third-party suite may be a reasonable choice if a particular product offers an extra feature you want or has test results and usability that suit your priorities. The lab results above show that some alternatives matched Defender’s protection and usability scores and scored higher on performance in that comparison; they do not show that every paid product is better.
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- Stay with Defender if you want a built-in baseline and do not have a specific reason to add another suite.
- Compare alternatives if you want features beyond Defender or prefer a product’s tested tradeoffs.
- Check the product version and recent independent results, along with current price, renewal terms, and device coverage, before buying. The cited test results do not establish current prices or plan limits.
Can Defender and another antivirus run together?
Do not plan to run two active antivirus engines at once. Microsoft says that when a compatible third-party antivirus app is installed and turned on, Microsoft Defender Antivirus turns off automatically; if that app is uninstalled, Defender turns back on. Microsoft documents how Defender Antivirus behaves alongside another antivirus app.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What should you do to keep a Windows 11 PC protected?
Keep Windows and your software updated, leave protection enabled, and use care with downloads and links. Antivirus is one part of PC security; the sources cited here do not quantify how much any one of those habits changes risk.
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Rank #4
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