An ad blocker for Firefox that fills the gaps

What Firefox already does

Firefox ships with built-in content blocking, which cuts a good share of trackers and third-party cookies out of the box. For everyday browsing that already removes a lot of clutter, and many users are happy with it alone.

Where a dedicated blocker still helps

Firefox's native protections don't neutralize video ads at the SDK level, so pre-roll ads can still appear on streaming and video-heavy sites. They also don't run a stealth layer, so some sites still detect blocking and show anti-adblock walls. And ad elements that slip through the network filters stay visible on the page.

AdOff adds exactly those layers: network blocking of ad requests, cosmetic filtering that hides leftover ad elements in the DOM, SDK-level video ad neutralization, and a stealth mode that keeps anti-adblock walls from triggering.

How AdOff works on Firefox

AdOff for Firefox is a Manifest V3 extension built on the same engine as the Chromium version: declarative network rules block requests to advertising networks, a stylesheet hides cosmetic ad leftovers, and a small in-page layer neutralizes video ad SDKs so players resume straight to content.

There's a technical detail worth knowing: Firefox doesn't support injecting scripts directly into the page's main world the way Chromium browsers do. AdOff ships a dedicated injector (stealth-injector.js) that bridges that gap, so the stealth anti-detection layer works on Firefox too — the same protection you get elsewhere, adapted to how Firefox actually works.

Installing AdOff on Firefox

Download adoff-firefox.zip from adoff.app, extract it, open about:debugging#/runtime/this-firefox and load the extension with "Load Temporary Add-on". The full step-by-step guide, with screenshots, is on the install page. AdOff requires Firefox 128.0 or later; make sure you pick the Firefox ZIP, not the Chromium one.

What changes compared to Firefox alone

With Firefox alone, you keep the browser's native tracker protection, but the page you see is still the page the site wants to show you: video players run their ad breaks, some sites gate content behind anti-adblock warnings, and banner leftovers survive the network filters. With AdOff on top, the ad requests are cut before they leave the browser, the visible leftovers are hidden from the page, video players skip straight to the content, and the stealth layer keeps the whole thing quiet. The browser stays the same Firefox you know — same interface, same settings, same speed feel — the pages it renders are simply cleaner.

Frequently asked questions

Does Firefox need an ad blocker?

Firefox blocks many trackers by default, but not video ads or anti-adblock walls, and some ad elements still get through. AdOff adds those layers on top.

How do I install AdOff on Firefox?

Download adoff-firefox.zip from adoff.app, extract it and load it from about:debugging with "Load Temporary Add-on". The complete walkthrough is on the install page.

Which Firefox versions are supported?

AdOff requires Firefox 128.0 or later. It's a Manifest V3 extension built on standard WebExtension APIs that Firefox 128+ supports.

Does AdOff for Firefox work on Android?

No. The Firefox build targets desktop Firefox only. There is no Android version of the extension at the moment.

Is AdOff for Firefox free?

Yes. AdOff is 100% free: the first 30 days need no account at all, and after that a free account is enough to keep every feature — network blocking, cosmetic filtering, video ad neutralization and stealth included.