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Do You Still Need Antivirus Software on Windows 11?

Windows 11 ships with its own antivirus and several other security layers. Here is what is already on your PC, how to check that it is working, what it does not cover, and when a third-party product is worth considering.

Independent guide. No partner links. Based on Microsoft’s official documentation, checked on 18 October 2026. Menu names can change slightly between Windows versions.

The short answer

You need antivirus protection, but on Windows 11 you already have it: Microsoft Defender Antivirus is built into Windows and is active when no other antivirus product is installed. Whether you also want a third-party product is a question of extra features and preferences, not of having “no protection” by default.

What Windows 11 includes

Windows Security and Microsoft Defender Antivirus

Windows Security is the app where you see and manage your protection. The antivirus engine behind it is Microsoft Defender Antivirus. It offers real-time protection, and quick, full, custom and offline scans. The offline scan restarts the computer and scans outside Windows, which can help with threats that are hard to remove while Windows is running.

Do not confuse it with the separate Microsoft Defender app, which Microsoft includes with Microsoft 365 Personal and Family subscriptions and which also runs on phones and Macs. You do not need that subscription to have the antivirus built into Windows.

Automatic updates

Microsoft Defender Antivirus downloads its latest security intelligence automatically through Windows Update. Windows Update also delivers the security fixes for Windows itself, which close vulnerabilities that malware could otherwise exploit. Keeping updates on is one of the most effective things you can do.

Microsoft Defender SmartScreen

SmartScreen warns you about websites reported for phishing or malware and checks downloaded apps and files against reputation data. A file that is not well known triggers a caution warning. Microsoft notes that SmartScreen protects against malicious files from the internet, not against files on internal network shares.

Smart App Control

On Windows 11 devices where it is available, Smart App Control lets apps run when Microsoft’s cloud service considers them safe, and blocks those considered malicious or potentially unwanted. When the service cannot decide, the app needs a valid signature to run. It is not available in S mode and may be turned off automatically, for example on managed or developer devices.

Tamper protection and ransomware protection

Tamper protection helps prevent malicious apps from changing important Defender settings such as real-time protection. Controlled folder access, found under Ransomware protection, prevents unknown apps from changing files in protected folders such as Documents, Pictures and Desktop once you enable it. Some legitimate apps may need to be allowed manually.

Firewall

Windows also includes a firewall, managed from the Firewall & network protection section of Windows Security.

How to check that your protection is on

  1. Open the Start menu, type Windows Security and open the app.
  2. Select Virus & threat protection.
  3. Under Who’s protecting me?, select Manage providers to see which antivirus product is active.
  4. Back in Virus & threat protection, open Manage settings and check that real-time protection and tamper protection are on.
  5. Open Settings → Windows Update and install pending updates.

Limits and good practices

Built-in protection is a solid base, but no security product, built-in or paid, can guarantee complete protection. Several risks depend mostly on habits:

  • Phishing and scams that persuade you to type a password or pay. Check the address bar and be wary of urgency.
  • Account takeover. Use unique passwords and turn on two-step verification for email, banking and work accounts.
  • Data loss. Keep a backup that is not permanently connected to your PC, and test a restore occasionally.
  • Outdated software. Update your browser and other apps, not only Windows.
  • Fake security alerts. A web page cannot scan your PC. Close pages claiming your computer is infected, and never call a phone number shown in such a pop-up.

Avoid turning real-time protection off to make a program work. Windows turns it back on automatically after a short while, and the better fix is to understand why the program was blocked.

When to consider a third-party product

  • You want to manage several devices, including Macs, Android phones or iPhones, from one place.
  • You want bundled extras you would actually use, such as a VPN, password manager or parental controls.
  • You prefer a different interface or support service.
  • You compared independent test results and a product suits your priorities, for example lower performance impact on an older PC.

If you install another antivirus, Microsoft documents that Microsoft Defender Antivirus switches to disabled mode automatically on a typical home PC, to avoid two products conflicting. If that product later expires or is uninstalled, Defender can switch back on automatically. After any change, check Manage providers again.

To weigh the cost of extra features, see Free vs Paid Antivirus: What Do You Actually Need?. For how to download and install any security product safely, read How to Choose Security Software for Your Computer.

A note for Windows 10 users

Microsoft ended support for Windows 10 on 14 October 2025. Without security updates for the operating system, antivirus alone is not enough, as Microsoft itself points out. Check Microsoft’s end-of-support page for upgrade or extended security update options for your device.

FAQ

Is Microsoft Defender enough for Windows 11?

For many home users, Microsoft Defender Antivirus with Windows Update, SmartScreen, a backup and good account security covers the essentials. “Enough” depends on your situation: the more devices, people and sensitive work you manage, the more useful extra tools and support can be.

Does Windows 11 have antivirus turned on by default?

Microsoft Defender Antivirus is built into Windows 11 and is in active mode when it is the only antivirus product. You can confirm it in Windows Security under Virus & threat protection → Manage providers.

Should I keep Defender if I install another antivirus?

You do not need to remove anything. On a typical home PC, Windows handles the switch automatically so that only one product provides real-time protection.

How do I run a deeper scan?

In Windows Security, open Virus & threat protection → Scan options and choose a full scan, or the Microsoft Defender Antivirus (offline scan). Save your work first: the offline scan restarts the computer.

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