Fix Windows Firewall Not Starting or Working

If Windows Firewall won’t start or stops working, the fix usually involves resetting the service, checking for corrupted system files, or clearing a blocked registry key. This guide walks through the most common causes and step-by-step solutions for Windows 10 and Windows 11.

Why Windows Firewall Fails to Start

Windows Firewall is a built-in security feature that filters network traffic based on rules. When it fails, you might see errors like “Windows Firewall cannot start” or “Windows Defender Firewall service cannot be started.” Common causes include:

The Windows Defender Firewall service (mpssvc) is disabled or set to manual.
Third-party security software (antivirus or firewall) has taken over and disabled the Windows service.
Corrupted system files or a damaged registry entry for the firewall.
Malware or a recent system update changed service settings.
Group Policy or local security policy overrides.

Step 1: Check the Firewall Service

The first thing to do is verify that the Windows Defender Firewall service is running. Press Win + R, type services.msc, and press Enter. Find Windows Defender Firewall in the list. Its status should be “Running” and the startup type should be “Automatic.” If it’s not, right-click it, select Properties, set the startup type to Automatic, click Start (if the service is stopped), then click OK. If the service fails to start, note the error message—it might point to a specific issue.

Step 2: Reset the Firewall Service via Command Line

If the service is already set to Automatic but still won’t start, you can try resetting it with elevated commands. Open Command Prompt as administrator (search for “cmd”, right-click, select “Run as administrator”). Then run these commands one by one:

net stop mpssvc (if it’s running)
net start mpssvc

If you get an error like “The service name is invalid,” the service may be corrupted. In that case, run sfc /scannow to repair system files, then try again. If that doesn’t help, run DISM /Online /Cleanup-Image /RestoreHealth to fix the Windows image, then restart and retry.

Step 3: Edit the Registry (Advanced)

Sometimes the firewall service’s registry key gets corrupted. This is an advanced step—back up your registry first (File > Export in regedit). Open regedit as administrator and navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\mpssvc

Check the Start value. It should be 2 (which means Automatic). If it’s 4 (Disabled), change it to 2, close regedit, and restart your computer. If the mpssvc key is missing entirely, you may need to restore it from a backup or use System Restore to a point before the problem started.

Step 4: Check for Third-Party Conflicts

Many third-party antivirus programs (like Norton, McAfee, or Bitdefender) include their own firewall and may disable Windows Firewall to avoid conflicts. If you have such software installed, check its settings to see if it has a “Windows Firewall” toggle or a “Firewall Protection” option. Some programs offer a “coexistence” mode. If you uninstall the third-party software, Windows Firewall should automatically re-enable itself. If it doesn’t, repeat Steps 1–3 after uninstalling.

Step 5: Use the Windows Security App

If the service is running but the firewall still appears off, try resetting it from the Windows Security app. Go to Settings > Privacy & Security > Windows Security > Firewall & network protection. Click Restore settings (if available) or toggle each network profile (Domain, Private, Public) to On. If the toggles are greyed out, it’s likely due to Group Policy or third-party software—see Step 4.

Step 6: Run the Windows Firewall Troubleshooter

Windows includes a built-in troubleshooter for network and firewall issues. Go to Settings > System > Troubleshoot > Other troubleshooters (or search for “troubleshoot” in the Start menu). Find Network Adapter or Incoming Connections and run it. This can automatically detect and fix common problems like blocked ports or misconfigured rules.

Frequently Asked Questions

Why does Windows Firewall keep turning off?

If it turns off automatically, it’s usually because third-party security software is disabling it, or a Group Policy setting is forcing it off. Check your antivirus settings first, then run gpedit.msc (Pro/Enterprise) and navigate to Computer Configuration > Administrative Templates > Windows Components > Windows Defender Firewall to see if any policy is set to “Disabled.”

Can I reset Windows Firewall to default settings?

Yes. In the Windows Security app, go to Firewall & network protection and click Restore firewalls to default. This resets all rules to their original state, which can fix misconfiguration issues. Note that this removes any custom rules you’ve added.

What does “Windows Firewall is using incompatible settings” mean?

This error usually appears when the firewall service is running but a required component (like the Base Filtering Engine) is not. Restart the Base Filtering Engine (BFE) service in services.msc, then restart the firewall service. If that fails, run SFC and DISM as described in Step 2.

Is it safe to disable Windows Firewall temporarily?

Disabling the firewall for a short time to test network issues is generally safe if you’re on a trusted network and have another firewall active. However, leaving it off exposes your system to network-based attacks. Always re-enable it immediately after testing.

Why can’t I start the Windows Defender Firewall service manually?

If the service won’t start manually, it’s often because the Base Filtering Engine service is stopped or disabled. BFE is a dependency—set it to Automatic and start it, then try starting the firewall service again. If BFE is corrupted, you may need to perform a system repair.

Does resetting the firewall affect my internet connection?

Resetting the firewall to defaults can temporarily block apps that relied on custom inbound rules, but your outbound internet connection usually works fine. After a reset, you may need to re-allow apps that request permission to communicate through the firewall.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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