Pop-up windows are windows that appear on top of the window you're using. While pop-up windows have valid uses, they are often used for annoying advertisements. Firefox comes with a pop-up blocker that's designed to block the unwanted pop-ups while still allowing the valid ones.

Table Of Contents

• Turning the pop-up blocker on or off
• How to know when a pop-up is blocked
• Allowing blocked pop-ups
• Pop-ups not being blocked
• Is the pop-up coming from Firefox?
• Is the pop-up blocker on and enabled for this site?
• Check again, is the pop-up blocker on?
• Is the pop-up shown after a mouse click or a key press?
• Is it a true pop-up window?

Turning the pop-up blocker on or off

Firefox's pop-up blocker is on by default. It can be enabled or disabled in Firefox's Options window.

1. Open the Firefox options panel.
   • (Windows) At the top of the Firefox window, click on the Tools menu, and select Options....
   • (Mac) On the menu bar, click on the Firefox menu, and select Preferences....
   • (Linux) At the top of the Firefox window, click on the Edit menu, and select Preferences....
2. Click the Content icon. The Content panel is displayed.
3. Use the Block pop-up windows checkbox to enable or disable the pop-up blocker.

How to know when a pop-up is blocked

When a pop-up is blocked, Firefox will show a yellow bar at the top of the webpage with the text Firefox prevented this site from opening a popup window..

Allowing blocked pop-ups

You can allow a web site to display a pop-up that Firefox blocked. You can also set Firefox to always allow pop-ups from a web site.

To display a single blocked pop-up:

1. On the yellow bar, click Options or Preferences.
2. Click Show http://.... The pop-up will now appear.

To allow a site to always show pop-ups:

1. On the yellow bar, click Options or Preferences.
2. Click Allow pop-ups for.... The pop-ups that were blocked will not appear, but any future pop-ups from that site will be allowed.

To remove a site from the allowed pop-up list:

1. Open the Firefox options panel.
   • (Windows) At the top of the Firefox window, click on the Tools menu, and select Options....
   • (Mac) On the menu bar, click on the Firefox menu, and select Preferences....
   • (Linux) At the top of the Firefox window, click on the Edit menu, and select Preferences....
2. Click the Content icon. The Content panel is displayed.
3. To the right of Block pop-up windows, click the Exceptions... button. A dialog will appear that shows all the sites that are allowed to show pop-ups.
4. To remove a site from the list, click on its row, then click Remove Site.

Pop-ups not being blocked

Is the pop-up coming from Firefox?

The pop-up may not actually be coming from Firefox. You can determine where the pop-up is coming from by the icons it has and the title at the top.

• A Firefox icon and "Mozilla Firefox" in the title: keep reading below.
• "Messenger Service": read this article at Microsoft.com
• Everything else: you may have malware on your computer that causes the pop-ups. Scan your computer for viruses and spyware.

This pop-up comes from Firefox. It has a Firefox icon and the text Mozilla Firefox.

Is the pop-up blocker on and enabled for this site?

1. Open the Firefox options panel.
   • (Windows) At the top of the Firefox window, click on the Tools menu, and select Options....
   • (Mac) On the menu bar, click on the Firefox menu, and select Preferences....
   • (Linux) At the top of the Firefox window, click on the Edit menu, and select Preferences....
2. Click the Content icon. The Content panel is displayed.
3. Make sure the Block pop-up windows checkbox is checked.
4. To the right of Block pop-up windows, click the Exceptions... button. A dialog will appear that shows all the sites that are allowed to show pop-ups.
5. If the site that's opening pop-ups is in the list, click on it and press Remove Site.
6. Press Close.
7. Press Close.

Check again, is the pop-up blocker on?

McAfee Privacy Service can disable Firefox's pop-up blocker to be able to use its own. Even if you try to turn Firefox's pop-up blocker on, the next time you open the Firefox options panel, it'll be off again. If you uninstall McAfee Privacy Service, the problem will remain.

1. Open the Firefox options panel.
   • (Windows) At the top of the Firefox window, click on the Tools menu, and select Options....
   • (Mac) On the menu bar, click on the Firefox menu, and select Preferences....
   • (Linux) At the top of the Firefox window, click on the Edit menu, and select Preferences....
2. Click the Content icon.
3. If the Block pop-up windows box is no longer checked, McAfee Privacy Service may be turning it off.

If you still McAfee Privacy Service installed, turn off its pop-up blocker feature and restart your computer. You should now be able to turn Firefox's pop-up blocker on.

If you no longer have McAfee Privacy Service, you will need to edit your Firefox configuration file.

1. Open Notepad (or any other text editor).
2. In Notepad, browse to your profile folder and open the user.js file.
3. Erase the line that says

   user_pref("dom.disable_open_during_load", false);

4. Save the file.
5. Restart Firefox.

You should now be able to turn Firefox's pop-up blocker on.

Is the pop-up shown after a mouse click or a key press?

Certain events, such as clicking or pressing a key, can spawn pop-ups regardless of if the pop-up blocker is on. This is so that Firefox doesn't block pop-ups that web sites need to work.

Is it a true pop-up window?

Sometimes ads are designed to look like windows, but really aren't. Firefox's pop-up blocker can't stop these ads.

This page has fake pop-up windows. Some signs include the color of the title bars being wrong and an incorrect or missing icon in the top left.