Does Firefox block ads by default?
Not in a normal window. Mozilla points readers who want an ad blocker to add-ons. What Firefox has on, by default since 2019, is Enhanced Tracking Protection at Standard: it blocks social media tracking cookies, fingerprinters and cryptominers, keeps cookies to each site (Total Cookie Protection, since 2022) and blocks tracking content only in private windows.
| Standard, normal window (the default) | Standard, private window | Strict, any window | |
|---|---|---|---|
| Ads from networks on the tracking list, Google's ad domains among them 3 | Load | Blocked | Blocked |
| Analytics on the list, Google Analytics included 3 | Loads | Blocked | Blocked |
| Third-party cookies 4 | Kept to each site | Kept to each site | Kept to each site |
| Fingerprinters and cryptominers 2 | Blocked | Blocked | Blocked |
| Embedded content on the list (videos, comments) 2 | Loads | Loads | Blocked, save Firefox's fixes |
Blocked: save Mozilla's exceptions to fix broken sites; what you serve from your own domain is not on the list. Read November 2, 2026; numbers: Sources.
Brave works the other way and blocks third-party ads in every window: what Brave and Safari block by default.
What private windows and Strict mode take out of your page
Tracking content, in Mozilla's words, is outside ads, videos and other content that carry tracking code, from companies on a list maintained by Disconnect that Mozilla reviews: private windows apply the base list, and Strict applies it in every window, with a longer one.
The base list has an Advertising category, and Google's ad domains, those of AdSense and Ad Manager, are in it. Where it applies, Mozilla says your site won't be able to use "third-party advertising or analytics services that engage in tracking."
- Includes
- Google's ad domains: AdSense and Ad Manager
- Applied in
- private windows; every window on Strict
- Publisher allowlist
- none
Strict is the reader's choice, and Mozilla notes some sites may need adjustments. Mozilla only lifts blocking to fix broken sites, and the reader can switch the protection off for one site from the shield.
What the list does not cover
Firefox applies the list only to third parties on it, so what your own domain serves is outside it; Google's ad tags load from Google's domains, which are on it.
Does uBlock Origin still work on Firefox? Yes, in full
On Chrome, the full uBlock Origin no longer runs: Chrome readers get uBlock Origin Lite. Firefox kept the older extension platform, Manifest V2, alongside the new one; Mozilla has no plans to retire it and confirmed it in February 2025. So the full uBlock Origin, a Mozilla-recommended add-on, runs on Firefox in full.
No plans to retire Manifest V2; at least 12 months' notice before any change
Firefox keeps the platform the full uBlock Origin needs, which Chrome removed
Firefox on Android and iPhone: extensions on one, an optional ad blocker on the other
| Desktop | Android | iPhone | |
|---|---|---|---|
| Extensions | Yes, the full uBlock Origin included | Yes | No Firefox extensions |
| Own ad blocker | None | None | Yes, off by default (version 156) |
| Tracking protection | Standard by default | Standard by default | Yes, its own |
Firefox for Android has the same protection and takes extensions, open to all compatible ones since December 14, 2023. On iPhone and iPad, Firefox runs on Apple's WebKit with no add-ons; since version 156 (September 2026) it has an optional ad blocker built on EasyList, off until the reader turns it on. Mozilla says ads served by the site itself still show.
How many Firefox page views run a blocker?
Firefox 34.0%
Network average 23.7%
Page views with a blocker out of all page views on the sites that use AntiAdBlock Core, between August 28 and October 17, 2026. One network, not the market.
Firefox page views arrived with a blocker more often than the average (34.0% against 23.7%): a rate within Firefox, not its share of your traffic.
Fewer impressions, missing visits: where Firefox shows up in your reports
- Ad network report fewer impressions: private windows, Strict, extensions
- Analytics visits missing where Google Analytics is blocked
- Targeting less cross-site data in every window
An ad that does not load is never counted or paid for, and where Google Analytics is blocked the visit is missing too: it shows above all in your ad network's impressions.
Mozilla's own ads show in the browser, not on your page
Mozilla's ads stay in the browser itself, and the ad-measurement experiment of Firefox 128 has since been retired: none of it fills your ad slots.
Measuring and answering Firefox readers
AntiAdBlock Core runs on Firefox, desktop and Android, like on every major browser, with multi-signal detection maintained daily. Measuring comes with every plan; to act, you choose the wall or, on Max and Business, the Detection API.
- Measure
Your adblock rate in the dashboard; on Max and Business, also by browser and type, with Browser protection (Firefox and Edge) apart, as sample data on Free and Pro. It never names the reader's extension or protection level.
Plan: All plans; by type and browser, Max and Business
- Ask to allow your site
The notice is a wall from the first blocked page. With Firefox's protection, the Firefox wall shown here, with the desktop steps and in place of your own message on Max; Firefox on iPhone does not get it. With an extension, the usual wall.
Plan: All plans
- Handle it in your code
The Detection API detects and counts, shows no wall and hands your code the result, with the browser and the type of blocking (browser_protection for Firefox's own).
Plan: Max and Business
The wall on Firefox > two cases
Firefox's own protection
Firefox is blocking ads
Firefox's tracking protection (private window or Strict mode) is blocking ads on this site. You can turn it off for this site only with one click.
- Shield: click the shield icon left of the address bar and turn protection off for this site.
- Private window: open this page in a normal window.
- Settings: under Privacy and Security, switch protection from Strict to Standard.
An extension
The same wall as on any browser.
On a computer. Always a wall: it can't be closed.
Paid plans start at $5 a month (pricing); at the monthly quota, detection pauses until it resets or you upgrade. More in our anti-adblock script guide.
Firefox and ad blocking: publisher questions
Does Firefox block ads by default?
Not in a normal window: on desktop and Android it has no built-in ad blocker, and at Standard the big networks' ads load. Private windows and Strict mode block tracking content, many ads included. On iPhone, its optional ad blocker is off by default.
Does Firefox Strict mode block ads?
Yes, ads from networks on the tracking list, Google's ad domains among them, in every window, unless Mozilla has lifted blocking to fix a broken site. What your own domain serves is not on the list. Mozilla notes some sites may need adjustments.
Does Firefox block AdSense and Google Analytics?
Only in private windows and Strict mode, or with an extension: Google's ad domains are in the Advertising category of the Disconnect list Firefox applies there, Google Analytics in its Analytics category. Mozilla can lift blocking to fix a broken site, and your own domain is not on the list.
Does uBlock Origin still work on Firefox?
Yes, in full, on desktop and Android. Firefox supports Manifest V2 alongside V3: Mozilla has no plans to retire it, would give at least 12 months' notice, and in February 2025 confirmed it keeps both. On Chrome, readers only get uBlock Origin Lite.
Does AntiAdBlock Core work with Firefox?
Yes, on desktop and Android, like on every major browser; on Max and Business, the dashboard shows Firefox's own protection as Browser protection. The live demo shows the wall.
How does a Firefox reader allow my site?
On desktop, for Firefox's own protection, they click the shield left of the address bar and switch the protection off for your site; it stays on elsewhere. The AntiAdBlock Core wall gives those steps. With an extension, they allow your site from its button.
Sources
Mozilla documentation and lists, read on November 2, 2026; the rest are linked where they are cited.
- Mozilla Firefox: ad blocker features · read Nov 2, 2026
- Firefox source docs: Enhanced Tracking Protection by mode · read Nov 2, 2026
- Firefox tracking protection lists (shavar-prod-lists) · read Nov 2, 2026
- Total Cookie Protection by default · Jun 14, 2022 · read Nov 2, 2026
- Manifest V3 and Manifest V2, March 2024 update · Mar 13, 2024 · read Nov 2, 2026
- Mozilla's approach to Manifest V3 · Feb 25, 2025 · read Nov 2, 2026
- Firefox for iOS: the ad blocker · Sep 1, 2026 · read Nov 2, 2026
- AntiAdBlock Core Adblock statistics 2026 (our network data) · Oct 17, 2026
Measure the blocking on your site, Firefox included
Add one tag or the WordPress plugin and your adblock rate shows from the first page views; the split by browser and type comes with Max and Business.
Free plan: 5,000 detections a month, no payment method.
By AntiAdBlock Core