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Yes—you can install Malwarebytes on a Windows PC that has Microsoft Defender Antivirus, but having both apps installed does not mean both antivirus engines are actively protecting the device. Microsoft says a compatible third-party antivirus can automatically turn Defender Antivirus off. Check Windows Security’s provider status to see which antivirus Windows recognizes as active.
What “running both” means
“Windows Defender” usually refers to Microsoft Defender Antivirus, which is managed through the Windows Security app. It is different from the Microsoft Defender app offered with some Microsoft 365 subscriptions. Malwarebytes says its Windows app is designed to work with other antivirus software, so the apps can coexist on a PC. However, installation and active antivirus protection are separate questions: Windows may turn Defender Antivirus off when it recognizes a compatible third-party antivirus.
To check the status, open Windows Security, select Virus & threat protection, then choose Manage providers. Use the status shown there rather than assuming that both products are providing real-time antivirus protection. Microsoft says Defender Antivirus should return to active mode automatically after a non-Microsoft antivirus is uninstalled. Microsoft’s Windows Security guidance explains provider status and scan options.
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Yes. Malwarebytes’ Windows feature table, updated September 8, 2026, lists Quick Scan and Custom Scan as free features. The same table lists Threat Scan, Scheduled Scan, and Real-Time Protection as paid features. A free on-demand scan is not the same as running Malwarebytes’ paid real-time protection alongside Defender.
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Windows Security also provides quick, full, custom, and Microsoft Defender Offline scans, and lets you scan a selected file or folder. You can use Windows’ built-in scanning tools without treating Malwarebytes as a second active antivirus engine. See the Microsoft guide to staying protected with Windows Security for scan options.
Check compatibility before installing
Malwarebytes lists Windows 10 and Windows 11 as supported, with S mode disabled, at least 4 GB of memory, and 1 GB of disk space required at installation. These are the requirements listed in its Help Center; confirm the current requirements before installing, since support and compatibility details can change.
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Malwarebytes’ installation instructions cover downloading and installing the app, then activating it with an account, license key, or activation code. Follow the current Malwarebytes for Windows installation instructions.
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Malwarebytes identifies blocked applications, another antivirus stopping, loss of internet access, and Windows blue-screen errors as possible compatibility problems. Its guidance recommends adding each product to the other’s allow list where appropriate. This is troubleshooting advice, not a guarantee that every combination or PC configuration will work.
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- 24/7 REAL TIME PROTECTION against emerging malware threats, including ransomware and viruses- without slowing you down
- PROTECTS YOUR DEVICES ON MULTIPLE PLATFORMS: Get cyber protection for your computers, smartphones, or tablets- Compatible with Windows, Mac, Android, iOS devices
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If the problem involves network access or crashes, overlapping use of Windows Filtering Platform by web-protection features may be involved. Malwarebytes advises seeking help to disable the other antivirus’s website protection; if necessary, it also describes turning off Malwarebytes Web Protection. Disabling that feature reduces Malwarebytes’ web-protection coverage, so treat it as a diagnostic or compatibility trade-off, not a no-cost fix. If the products remain incompatible, Malwarebytes advises uninstalling the other antivirus.
For setup and allow-list guidance, see Malwarebytes’ instructions for adding Malwarebytes to the allow list in other apps and its instructions for adding items to Malwarebytes’ allow list.
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Choose a setup based on what you need
- For Windows’ built-in protection and scans: Keep Microsoft Defender Antivirus active and use Windows Security’s scan options.
- For an occasional second opinion: Malwarebytes Free offers the Quick Scan and Custom Scan features listed as free in its September 8, 2026 Windows feature table. Do not assume that this means Malwarebytes’ paid real-time protection is active.
- If you install Malwarebytes’ paid real-time protection: Check Windows Security > Virus & threat protection > Manage providers to confirm which product Windows recognizes as active, then watch for application, network, or stability issues.
Neither vendor’s guidance establishes that two active antivirus engines necessarily improve protection. Decide based on the features you need and the provider status Windows reports, not on the assumption that more active antivirus products always means better security.
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