IronFox

IronFox is a web browser built from Mozilla’s Firefox for Android, with its settings changed for privacy and security. It is made by a small team under the name IronFox OSS. In its README: “IronFox is a fork of Divested Computing Group’s Mull Browser, based on Mozilla Firefox. Our goal is to continue the legacy of Mull by providing a free and open source, privacy and security-oriented web browser for daily use.” Version 159.0 is built on Firefox 159.0 and introduces IronFox’s built-in app updater.

What it changes from Firefox

• No telemetry, crash reports or ads code. IronFox switches off Firefox’s data reporting and crash reporter, and removes the Adjust and Sentry libraries and Google’s Firebase push library. In this file, telemetry and health reports are locked off.
• No Google Play Services needed. Push notifications for websites work through UnifiedPush if you install a distributor app and turn it on; for passkeys it carries microG’s open-source replacement for Google’s FIDO library, which needs microG or a separate provider app on the phone.
• DuckDuckGo as the search engine, and Google, Bing, Yahoo and several others removed from the list.
• Encrypted DNS through Quad9’s DNS server, in Firefox’s strictest mode, so lookups don’t fall back to your network’s DNS.
• Strict tracking protection and HTTPS-Only mode are on.
• Google Safe Browsing stays on, “with a proxy to protect the privacy of users” that IronFox runs. You can turn it off under IronFox settings → Security.

Defaults worth knowing

From the settings in this version:

• JavaScript’s just-in-time compiler is off, “in order to improve security”. The FAQ says this “doesn’t cause a noticeable difference on most modern devices” but may slow some down; the switch is in IronFox settings → Security.
• WebGL is off, except on a list of sites IronFox keeps where turning it off breaks them.
• Browsing history isn’t remembered, and history, cache, download history and open tabs are cleared when you close the browser.
• Websites are asked for English and light mode, “to protect against fingerprinting”. Both can be changed in IronFox settings.
• Installing add-ons is off, apart from the uBlock Origin offer on first start.
• DRM video is off: “IronFox does not support Encrypted Media Extensions (EME)”, so services that need it won’t play until you turn it on.
• Fingerprinting protection uses Firefox’s newer protection, not the stricter resistFingerprinting mode, which the FAQ says is “NOT recommended or supported”.

IronFox is open about the limits: “IronFox can not defeat sophisticated fingerprinting. Nothing besides Tor Browser can.” and “Firefox-based web browsers, including IronFox, have security deficiencies when compared to Chromium. This is especially notable on Android.”

What goes online

IronFox publishes a list of the connections it makes at default settings. The updater added in 159.0 is not yet in that list. Besides the sites you visit:

• Mozilla’s servers, for add-on update checks and Remote Settings (block lists and certificate data), both hourly, the content-signature check at every start, and the push service.
• IronFox’s Safe Browsing proxy, at every start and every 30 minutes after.
• IronFox’s update service at releases.ironfoxoss.org, when the browser comes to the foreground and the default one-hour interval has elapsed. A copy installed from this site is not tied to a store IronFox recognises, so it downloads an available update immediately on any connection, including mobile data, then asks before installing. This connection is not yet in IronFox’s published list; both switches are under Settings → IronFox settings → Updates (see the questions below).
• Quad9’s DNS server, for every domain you open. Before 158.0.1 the default was Mullvad’s, which is being discontinued; IronFox says people who chose Mullvad get a notification asking them to switch.
• Mozilla’s add-ons site, once, if you keep uBlock Origin ticked in the first-start setup, and afterwards the filter-list servers uBlock Origin uses. IronFox sets uBlock Origin up with a list of filter sources from its own server, assets.ironfoxoss.org, which its published list leaves out.

Our tracker scan matches Mozilla Telemetry, on class names from Mozilla’s Glean library. IronFox explains that “while it’s untenable to fully remove all references to the Glean library, we do remove the Glean service library, and we stub the Glean library itself at build-time and break/neuter all of its functionality.”

About this file

• This is IronFox 159.0, released on 28 October 2026, the 64-bit ARM build from IronFox’s own F-Droid repository, which it describes as holding “official binaries built by IronFox OSS”. The file is byte for byte the one on IronFox’s release server, whose published SHA-512 it matches. It is signed by IronFox, with the certificate fingerprint IronFox publishes on its download page (C5:E2:91:B5…F9:04). IronFox also makes builds for 32-bit ARM and x86_64.
• IronFox isn’t on Google Play, and not in F-Droid’s main repository by its own choice: “We currently do not support IronFox’s inclusion in F-Droid’s official repository, due to what we feel are significant privacy and security concerns.”
• The 166.6 MB file needs Android 8.0 or later; IronFox’s download page still says Android 5, but the app itself requires 8.0. It declares 30 permissions, among them location, camera and microphone for sites that ask, notifications, and installing downloaded APK files.
• The browser code is Firefox’s, under the Mozilla Public License 2.0; IronFox’s build scripts are under the AGPL-3.0, and the preference settings it uses, from its Phoenix project, under the GPL-3.0. “Mozilla Firefox is a trademark of The Mozilla Foundation.” IronFox notes that it is “in no way affiliated with Mozilla”.
• The app is translated into Brazilian Portuguese.
• The screenshot is IronFox’s, from its F-Droid repository.

CPU types in this build: arm64-v8a (64-bit ARM, almost every phone since 2017).