Understanding and Disabling Firefox's Default Browser Agent

This article explains the purpose of the Mozilla Firefox Default Browser Agent in Windows and provides step-by-step instructions on how to disable it. You will learn why Mozilla introduced this background scheduled task, what data it collects, and the multiple methods available—including Firefox's advanced configuration, the Windows Task Scheduler, and telemetry settings—to permanently stop it from running on your system.

What is the Default Browser Agent?

Introduced in Firefox version 75, the Default Browser Agent is a background service that installs as a Windows Scheduled Task alongside the Firefox web browser. The primary purpose of this task is to monitor your Windows default browser settings.

Every 24 hours, the agent runs in the background to check which program is currently set as your system's default web browser, as well as what the previous default browser was. It then sends this information back to Mozilla.

Mozilla uses this telemetry data to understand user trends, specifically to see if users are intentionally switching away from Firefox or if Windows updates are forcefully resetting default browser preferences to Microsoft Edge. The agent runs even when Firefox is closed. It does not collect personal information, browsing history, or passwords; it only transmits operating system version, locale, and default browser configurations.

How to Disable the Default Browser Agent

If you do not want this background task running on your computer or sending data to Mozilla, you can disable it using any of the following methods.

Method 1: Using the Windows Task Scheduler

The most direct way to stop the agent from running at the operating system level is to disable it in the Windows Task Scheduler.

  1. Press the Windows Key + R on your keyboard to open the Run dialog box.
  2. Type taskschd.msc and press Enter to open the Task Scheduler.
  3. In the left-hand pane, expand the Task Scheduler Library folder.
  4. Click on the Mozilla folder.
  5. In the middle pane, locate the task named Firefox Default Browser Agent (it will be followed by a string of letters and numbers).
  6. Right-click on the task and select Disable (or Delete if you want to remove it entirely).

Note: Sometimes major Firefox updates may re-enable the task if you only delete it, so choosing "Disable" is generally more reliable.

Method 2: Using Firefox's Advanced Configuration (about:config)

You can tell Firefox to deactivate the agent directly through the browser's internal configuration page.

  1. Open the Firefox browser.
  2. Type about:config into the address bar and press Enter.
  3. Click the Accept the Risk and Continue button.
  4. In the search bar at the top, type default-browser-agent.enabled.
  5. Locate the preference in the results below. Double-click on it (or click the toggle icon on the right) to change its value from true to false.

Method 3: Disabling Firefox Telemetry

Because the Default Browser Agent relies on Firefox's telemetry system to send data, opting out of telemetry will prevent the agent from transmitting any information to Mozilla.

  1. Open the Firefox browser.
  2. Click the menu button (three horizontal lines) in the top-right corner and select Settings.
  3. Select Privacy & Security from the left-hand menu.
  4. Scroll down to the Firefox Data Collection and Use section.
  5. Uncheck the box next to Allow Firefox to send technical and interaction data to Mozilla.

Method 4: Using Windows Registry (Group Policy)

For system administrators or users who want a permanent, system-wide block that Firefox updates cannot overwrite, you can disable the agent via the Windows Registry.

  1. Press the Windows Key + R, type regedit, and press Enter.
  2. Navigate to the following path: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Mozilla\Firefox (If the Mozilla or Firefox keys do not exist, right-click the parent folder, select New > Key, and create them).
  3. Right-click in the right-hand pane and select New > DWORD (32-bit) Value.
  4. Name the new value DisableDefaultBrowserAgent.
  5. Double-click the new value, set its Value data to 1, and click OK.