How to keep MS Defender from turning off

Dear Peter Farrelly,

Thanks for contacting us on Microsoft Q&A. Let's work together to help you resolve this case effectively.

Regarding the Defender's protection repeatedly turning off and directing turning on in Accessibility. I found that the most causes related to Defender's requirement, such as for saving battery. Since Defender’s Web Protection feature relies on Accessibility access, it gets disabled when the permission is revoked.

Here is some solution that you can try: 

• Grant Required Permissions
  • Enable Accessibility Service (Required for real-time scanning)
  • Go to Settings > Accessibility > Installed apps (or Downloaded services)
  • Find Microsoft Defender and toggle it ON.
  • If asked, confirm by tapping OK or Allow.
• Enable App Autostart (Prevents Defender from being killed in the background)
  • Go to Settings > Apps > Microsoft Defender > Battery > Allow background activity (or Unrestricted).
• Disable Battery Optimization
  • Go to Settings > Apps > Microsoft Defender > Battery > Battery optimization.
  • Select All apps, find Microsoft Defender, and choose Don’t optimize.
• Check for Conflicting Security Apps: Other security apps (e.g., phone manufacturer's security center, third-party antivirus) might conflict with Defender or get priority. Try temporarily disabling/uninstalling others to test.
• Update Defender & Android OS: Ensure both your Microsoft Defender app and Android OS are updated to the latest versions. Older versions may have bugs.
• Reset Defender App (Last Resort):
  • Go to Settings > Apps > Microsoft Defender. Tap Storage & cache > Clear Cache. If unsuccessful, try Clear Storage/Clear Data (Warning: Clears app settings/logins - you'll need to sign back into your Microsoft account).
  • Uninstall Defender, reboot your phone, then reinstall the latest version from Google Play Store. Follow the steps above precisely to enable Accessibility permission.
• Enable Background Activity
  • Go to Settings > Apps > Microsoft Defender > Battery
  • Make sure Allow background activity is turned on Lock the App in Task Manager (if available)
  • On some devices (like Xiaomi or RealMe), swipe down on the app in the task switcher to lock it. This prevents the system from killing the app when clearing tasks

For your reference: https://support.microsoft.com/en-us/topic/web-protection-keeps-turning-off-on-my-android-device-d3891ea2-50db-430b-aac1-d752611ae5c9

I hope this help. Please feel free to reply back in this post if you need further assistance.

Kind regard,

Ami - Microsoft Q&A Support Specialist

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