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ActiveGecko engine 28/30 documented

Firefox Focus

Mozilla's deliberately minimal mobile browser that blocks trackers by default and is built around erasing the session rather than storing it.

Published by Mozilla (United States) Verified

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Runs on

  • macOSmacOS: Unavailable
  • WindowsWindows: Unavailable
  • LinuxLinux: Unavailable
  • AndroidAndroid: Available
  • iOSiOS: Available

Choose it when

Choose Firefox Focus as a secondary browser for searches and links you do not want retained, where erasing the session in one tap is the point.

Avoid it when

Avoid it as your only browser: there is no sync, no profiles, no extensions, and no tab management worth the name, all by design.

Quick answers

Read straight off the verified record - every one of these is expanded with its source below.

Which platforms does Firefox Focus run on?
Which platforms does Firefox Focus run on?
Documented on Android and iOS. Not available on macOS, Windows, and Linux.
Can I install Chrome extensions?
Can I install Chrome extensions?
No - the Chrome Web Store is not supported.
Does it block trackers out of the box?
Does it block trackers out of the box?
Yes - tracker or ad blocking is on by default. Tracker blocking is enabled by default.
Does it have built-in AI features?
Does it have built-in AI features?
No AI capability in this record is documented as built in.
Is it open source?
Open source under the Mozilla Public License
Is it still being developed?
Is it still being developed?
Active - Actively maintained with ongoing mobile releases.

What Firefox Focus does

Open any row for the wording and the source behind it

Privacy and tracking

2 built in · 1 partial · 1 not available

  • Blocks trackers by defaultBlocks trackers by default: Built in

    Tracker blocking is enabled by default.

  • Anti-fingerprintingAnti-fingerprinting: Built in

    Known fingerprinting scripts are blocked by default.

  • Telemetry postureTelemetry posture: Minimal or opt-in

    Mozilla documents limited data collection with user controls.

  • Built-in VPN or proxyBuilt-in VPN or proxy: Unavailable
  • Private windowsThe whole browser behaves as a private session; a single action erases history, cookies, and passwords.

    The whole browser behaves as a private session; a single action erases history, cookies, and passwords.

  • Default search engineConfigurable

Extensions and blocking

1 built in · 4 not available

  • Chrome Web StoreChrome Web Store: Unsupported
  • Firefox Add-onsFirefox Add-ons: Unsupported
  • Native content blockingNative content blocking: Built in

    Ad and tracker blocking are built in and on by default.

  • Manifest V3Manifest V3: Unavailable
  • Manifest V2Manifest V2: Unavailable
  • Known limitationsThe product deliberately omits an extension platform; blocking is built in instead.

    The product deliberately omits an extension platform; blocking is built in instead.

Workflow

9 not available · 2 undocumented

  • Vertical tabsVertical tabs: Unavailable
  • Tab treesTab trees: Unavailable
  • Workspaces or spacesWorkspaces or spaces: Unavailable
  • ProfilesProfiles: Unavailable

    No profile system is provided.

  • Split viewSplit view: Unavailable
  • SidebarSidebar: Unavailable
  • Reader modeReader mode: Unavailable

    No reader view is provided.

  • Command paletteCommand palette: Unavailable
  • Sync across devicesSync across devices: Unavailable

    No account sync is provided.

  • TranslationTranslation: Unknown

    Translation is not documented.

  • Progressive web appsProgressive web apps: Unknown

    Progressive web app behaviour is not documented.

AI features

9 not available

  • Built-in assistantBuilt-in assistant: Unavailable
  • Page summarisationPage summarisation: Unavailable
  • Acts on pages for youActs on pages for you: Unavailable
  • AI answer engineAI answer engine: Unavailable
  • Works across open tabsWorks across open tabs: Unavailable
  • Text or image generationText or image generation: Unavailable
  • Choice of modelChoice of model: Unavailable
  • Retention or training controlsRetention or training controls: Unavailable
  • Voice or image inputVoice or image input: Unavailable

On a phone

2 built in · 1 not available · 7 undocumented

Undocumented is not the same as absent - it means the publisher does not state it.

  • Extensions on mobileExtensions on mobile: Unavailable

    Focus is deliberately not an extensions browser.

  • Can be the phone defaultCan be the phone default: Built in

    Mozilla documents making Focus the default browser on both Android and iOS.

  • Biometric lockBiometric lock: Unknown

    Biometric locking is not documented.

  • Offline readingOffline reading: Unknown

    Offline reading is not documented.

  • Desktop-site modeDesktop-site mode: Built in

    A desktop view control is documented in Focus help.

  • Download managerDownload manager: Unknown

    A built-in download manager is not documented.

  • Background playbackBackground playback: Unknown

    Background or picture-in-picture playback is not documented.

  • Web pushWeb push: Unknown

    Web push support is not documented.

  • Data saverData saver: Unknown
  • Address-bar placementAddress-bar placement: Unknown

    Address-bar placement is not documented.

Under the hood

Rendering engine
Gecko
JavaScript engine
SpiderMonkey
Upstream project
Mozilla Firefox
Release channel
stable
Code and licence
Open source under the Mozilla Public License
Install method
Platform app store.
Hardware support
No specific CPU requirements are documented.
Source repository

Active. Actively maintained with ongoing mobile releases.

Editorial view

Firefox Focus is the rare product that is easier to describe by what it refuses to do. There is no sync, no profile system, no extension platform, no reader view, and no attempt at tab management. What it has instead is tracker blocking on by default, fingerprinting-script blocking, and a single prominent action that erases history, cookies, and passwords. The erase button is the interface, not a setting buried in a menu.

The shape of it

Mobile-only, on Android and iOS, actively maintained by Mozilla alongside the main Firefox apps. Telemetry is documented as limited with user controls, a stronger statement than most vendors make and weaker than the outright removal the hardened forks perform.

The engine fact people get wrong

On Android, Focus renders with Gecko through GeckoView. On iOS it does not: Apple's rules keep every App Store browser on WebKit, so installing Focus on an iPhone is a way to get Mozilla's blocking defaults and erase behaviour on top of Apple's engine, not a way to run Mozilla's engine. That distinction matters to anyone choosing it for engine diversity reasons.

No extensions is the design

Blocking that other browsers delegate to add-ons is built in, and the product's simplicity depends on not having an add-on surface. If you want uBlock Origin, a password manager, and a custom filter list, Focus is the wrong tool and Firefox for Android, which does support add-ons, is the right one from the same vendor.

Where it fits

As a second browser, not a first:

  • Searches you would rather not have follow you around
  • Links from messages you do not want in your main history
  • A shared phone where the last session should not be visible to whoever picks it up next

In that role the lack of sync and profiles is a feature: nothing persists, so nothing needs managing. As a primary browser it would be actively annoying, and Mozilla does not pretend otherwise. It can be set as the platform default on both systems, which is worth knowing if you want every tapped link to land somewhere that forgets it.

Where these facts come from

Every capability above is read from a primary source and dated. 2 of 30 fields stay recorded as unknown rather than assumed.

If this is not it

Alternatives to Firefox Focus

Head to head

Reviewed comparisons featuring Firefox Focus