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ActiveGecko engine 28/30 documented

Tor Browser

A Firefox-based browser configured to route browsing through Tor and reduce linkability.

Published by The Tor Project (United States) Verified

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Runs on

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

Choose it when

Choose Tor Browser when reducing network linkability and browser fingerprint uniqueness is the primary requirement.

Avoid it when

Avoid it as a daily drop-in when you need maximum speed, unrestricted extensions, persistent profiles, or sites that reject Tor traffic.

Quick answers

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

Which platforms does Tor Browser run on?
Which platforms does Tor Browser run on?
Documented on macOS, Windows, Linux, and Android. Not available on iOS.
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. Tor Browser includes anti-tracking and isolation controls.
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 Firefox-derived project under MPL-compatible licensing
Is it still being developed?
Is it still being developed?
Active - Actively maintained by the Tor Project with security-focused releases.

What Tor Browser does

Open any row for the wording and the source behind it

Privacy and tracking

3 built in · 1 not available

  • Blocks trackers by defaultBlocks trackers by default: Built in

    Tor Browser includes anti-tracking and isolation controls.

  • Anti-fingerprintingAnti-fingerprinting: Built in

    Letterboxing and standardization help reduce fingerprinting uniqueness.

  • Telemetry postureTelemetry posture: Unavailable

    The Tor Project states it does not use tracking, telemetry, or analytics; leftover upstream telemetry code is disabled.

  • Built-in VPN or proxyBuilt-in VPN or proxy: Built in

    Tor routing is the browser's defining network feature; it is not a VPN.

  • Private windowsTor Browser windows use private-style behavior by default and route through Tor; Tor is not protection against every endpoint attack.

    Tor Browser windows use private-style behavior by default and route through Tor; Tor is not protection against every endpoint attack.

  • Default search engineDuckDuckGo

Extensions and blocking

1 built in · 2 partial · 1 not available · 1 undocumented

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

    NoScript and other Tor configuration controls provide native anti-tracking behavior.

  • Manifest V3Manifest V3: Unknown

    Do not infer ordinary Firefox extension compatibility from Tor Browser hardening.

  • Manifest V2Manifest V2: Available by extension

    Only the bundled and compatible Firefox extension model should be assumed.

  • Known limitationsInstalling extra extensions can change fingerprinting and security properties and is discouraged unless understood.

    Installing extra extensions can change fingerprinting and security properties and is discouraged unless understood.

Workflow

4 built in · 6 not available · 1 undocumented

  • Vertical tabsVertical tabs: Built in

    Tor Browser 15 on the Firefox ESR 140 base includes native vertical tabs and the updated sidebar.

  • Tab treesTab trees: Unavailable
  • Workspaces or spacesWorkspaces or spaces: Unavailable
  • ProfilesProfiles: Built in

    Profiles or equivalent browser identities are available.

  • Split viewSplit view: Unavailable
  • SidebarSidebar: Built in

    Firefox sidebar features remain available with Tor-specific constraints.

  • Reader modeReader mode: Built in

    Firefox Reader View is available.

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

    Account sync is intentionally not a standard Tor Browser workflow.

  • TranslationTranslation: Unknown

    Translation can affect fingerprinting and is not treated as a guaranteed feature.

  • Progressive web appsProgressive web apps: Unavailable

    Installable web apps are not exposed on the ESR base Tor Browser ships.

AI features

9 not available

  • Built-in assistantBuilt-in assistant: Unavailable

    Tor Browser documents removing Mozilla's AI features as un-auditable.

  • 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

10 undocumented

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

  • Extensions on mobileExtensions on mobile: Unknown

    Extension support on mobile is not documented.

  • Can be the phone defaultCan be the phone default: Unknown

    Default-browser capability is not documented.

  • Biometric lockBiometric lock: Unknown

    Biometric locking is not documented.

  • Offline readingOffline reading: Unknown

    Offline reading is not documented.

  • Desktop-site modeDesktop-site mode: Unknown

    Desktop-site mode is not documented.

  • 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 ESR
Release channel
stable
Code and licence
Open source Firefox-derived project under MPL-compatible licensing
Install method
Official signed download or Android app store.
Hardware support
Use official downloads and verify signatures where practical.
Source repository

Active. Actively maintained by the Tor Project with security-focused releases.

Editorial view

Tor Browser exists for one job: making your traffic hard to trace and your browser hard to distinguish from every other Tor Browser. Everything about it follows from that job, including the parts that make it a poor daily driver. It is a Firefox ESR derivative maintained by the Tor Project, currently on the ESR 140 base, with official signed builds for macOS, Windows, Linux, and Android, and no iOS app.

The configuration is the product

  • Traffic routes through the Tor network by design
  • Letterboxing and standardised settings push every user toward one shared fingerprint
  • NoScript ships bundled, anti-tracking isolation is on, and the whole browser behaves like a private session
  • No telemetry; the Tor Project states it collects none, and leftover upstream telemetry code is disabled
  • DuckDuckGo is the default engine

Because the base is ESR 140, native vertical tabs and the modern sidebar are here too, along with Reader View. Sync is deliberately absent, translation is not guaranteed, and web-app installs are not exposed.

The rules of use

These matter more than the feature list.

  • Do not install extensions. Every one makes your install more distinguishable, which defeats the fingerprint work.
  • Do not resize the window carelessly, and do not log into accounts that identify you while expecting anonymity.
  • Tor routing is not a VPN, and neither protects a compromised endpoint.
  • Expect breakage: sites that block Tor exits will fail, and network round-trips make everything slower.

The verdict

Narrow on purpose. Reach for Tor Browser when reducing network linkability is the actual requirement: sensitive research, circumventing surveillance, anything where who-is-reading-this matters. Keep a conventional browser for everything else rather than trying to live in it. If what you want is Tor's anti-fingerprinting engineering for ordinary browsing on your own VPN, that is exactly what Mullvad Browser is, and if you just want strong daily defaults, LibreWolf costs far less friction. Use official downloads, verify signatures when practical, and resist the urge to customise, because a stock install is the whole point. Updates track the ESR schedule, and the browser prompts for restarts when one lands; take those seriously, since fixes here are security fixes.

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

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Head to head

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