Unwanted pop-ups in Firefox usually mean a setting changed, an extension interfered, or a redirect slipped past the built-in filter. Firefox blocks pop-ups by default, but the checkbox can be toggled off or bypassed.
This guide covers where to re-enable the blocker, how to allow pop-ups for trusted sites without turning off protection everywhere, and what to check when windows still keep opening.
In this guide, I have covered:
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Why Firefox still shows pop-ups when blocking is on
If Firefox is opening windows you did not ask for, the built-in blocker is probably still enabled. Firefox blocks pop-ups by default on every recent desktop release, but it intentionally allows pop-ups you trigger with a click or key press. Blocking those would break normal site behavior.
Aggressive ads, redirect chains, and outdated copies of Firefox can also get past the filter. Every fix lives in Firefox’s own settings. Mozilla’s pop-up blocker documentation confirms the same default behavior.
Enable Firefox’s built-in pop-up blocker
If new windows have started opening on their own, the first thing to check is the main pop-up blocker. It sits one menu deep in Firefox.
Click the hamburger menu 
at the top right and choose Settings. On macOS, click Firefox in the menu bar and select Preferences. That opens the same Settings page.
In the left sidebar, click Privacy & Security. Scroll to the Permissions section and tick Block pop-up windows if it is empty. Firefox saves the change right away. No restart is needed.
A fresh Firefox profile has this checkbox ticked. An empty box usually means a previous user, an extension, or a sync from another device turned it off. For a screenshot-driven walkthrough, see our guide on allowing or blocking pop-ups and redirects in Firefox on a computer.
Allow pop-ups on specific trusted sites
Some sites still open legitimate pop-up windows for login flows, payment confirmations, or downloads. The exceptions list lets you allow those sites without weakening protection everywhere else.
Stay on the Privacy & Security page and click Exceptions… next to Block pop-up windows. A small dialog opens with an Address of website field.
Type the full URL you want to allow, such as https://example.com, and click Allow. Repeat for other trusted sites, then click Save Changes. Pop-ups from those sites open normally. Every other site stays blocked.
You’ll know it worked when the site opens its pop-up and Firefox shows no blocked pop-up notification.
To remove an exception later, return to the dialog, select the entry, and click Remove Site.
Use the about:preferences shortcut
If you would rather skip the menus, Firefox has a direct address that jumps to the Privacy & Security panel.
Type about:preferences#privacy in the address bar and press . The Settings tab opens at the right section, where you can toggle the blocker or manage exceptions without clicking through the menu.
TIP: Bookmark this address or pin the Settings tab. It is the fastest way back to the Permissions block when a site asks for pop-up access.
What to do if pop-ups still appear
If Block pop-up windows is ticked and unwanted windows keep opening, work through these checks in order.
Update Firefox. An outdated build can miss the latest blocking rules. Open Settings and scroll to Firefox Updates at the top of the General page, then apply any pending update. Our Firefox download and update guide covers every desktop platform.
Check your extensions. Privacy or popup stopper extensions can override the built-in rule. Disable them one at a time from about:addons and reload the offending site. That tells you whether an add-on is getting in the way.
Clear site data. A stuck cookie can keep an old allowed state for a domain. Follow our Firefox cookies and cache guide to wipe stored site data, then revisit the page. For more control over cookies, see how to block or allow browser cookies in Firefox on a computer.
Check your other devices. The desktop setting does not sync to mobile. If you also browse on iPhone, see how to allow or block pop-ups in Firefox on iPhone to keep behavior consistent across devices.
Frequently Asked Questions
Is pop-up blocking enabled by default in Firefox?
Yes. A fresh install of Firefox on Windows, macOS, or Linux has the Block pop-up windows checkbox ticked under Settings → Privacy & Security → Permissions. You only need to open that page if the setting was changed, an extension disabled it, or a device sync turned it off.
Why do some pop-ups still appear even when blocking is on?
Firefox intentionally allows pop-ups that open as a direct result of a click or key press, such as login dialogs and open-in-new-window buttons. Advertisers may also try to open a window the moment you land on a page. Firefox blocks the ones it can match against its filter list.
How do I allow pop-ups on just one website?
Open Settings → Privacy & Security, click Exceptions… next to Block pop-up windows, type the site URL, click Allow, then Save Changes. That site joins your allow list and stays there until you remove it.
Does the Firefox pop-up blocker also stop tab redirects?
Some redirect chains that open new windows are filtered, but Firefox does not treat every redirect as a pop-up. If you keep being redirected against your will, disable suspect extensions, scan for malware, and clear cookies for the affected site.
How do I know if Firefox blocked a pop-up?
Firefox shows a small notification bar at the top of the page with an Options button whenever it blocks a pop-up. From there, you can allow the site for the current visit, add it to your exceptions list, or view the blocked request.
