Mozilla Firefox

Description

Mozilla Firefox is a free, open-source web browser created by Mozilla, a nonprofit organization with a mission focused on ensuring that the internet is open, accessible and privacy-respecting. Firefox was developed by Dave Hyatt and Blake Ross as an experimental offshoot of the Mozilla Application Suite and was first released to the public as version 1.0 on November 9, 2004. It soon found users as a faster, more standards-compliant competitor to Internet Explorer, and reached a peak desktop market share of over 32% in 2009. As of early 2025, Firefox has a market share of about 6% of the desktop browser market.

Firefox is based on Mozilla’s own Gecko rendering engine and SpiderMonkey JavaScript engine, and is the only major browser apart from Safari that does not use Google’s Blink. This independence allows Mozilla to implement privacy features and web standards on its own terms. New major versions are released every four weeks.

PLATFORMS and RELEASE CHannels

Firefox is available for Windows 10 and later (32-bit and 64-bit), macOS 10.15 or later, both Intel and Apple Silicon, and 64-bit Linux. Support for 32-bit Linux was dropped in Firefox 145 in November 2025, with those users being directed to the Firefox 140 ESR branch. On Android, Firefox requires Android 5.0 or higher and uses GeckoView engine, which is the same Gecko core wrapped in a reusable library for mobile apps. On iOS, Firefox requires iOS 16 or later and, like all third-party browsers for iOS, uses Apple’s WebKit engine instead of Gecko. Firefox is also available on ChromeOS via the Google Play Store.

Firefox has four release channels: Nightly (daily builds), Developer Edition (six to eight weeks ahead of stable, geared towards web developers), Beta (near final preview), and Stable (production release). The Extended Support Release (ESR) is a separate track for organizations who require longer support windows. ESR branches get security fixes for approximately one year. The current ESR base is Firefox 140. Firefox 115 ESR will continue to receive security updates until March 2026 for users on Windows 7, 8, 8.1, and macOS 10.12-10.14.

PRIVACY and TRACKing Protection

Privacy is the defining characteristic of Firefox. Enhanced Tracking Protection (ETP) enabled by default, using a list of known trackers maintained by Disconnect.me to block cross-site tracking cookies, social media trackers, fingerprinting scripts, cryptominers, and redirect trackers. ETP has three modes: Standard (the default), which blocks trackers on sites that have not been visited yet allows most site functionality; Strict, which blocks more broadly at the expense of occasional site breakage; and Custom, which allows users to choose exactly which categories to block.

Total Cookie Protection, also on by default, limits cookies set by each website to a different jar, so that third-party trackers cannot read cookies set by other websites. This avoids the cross-site cookie tracking that has been standard in online advertising for decades.

Firefox 145, released in November 2025, introduced a big new phase of anti-fingerprinting protections. Browser fingerprinting gathers subtle technical information — screen resolution, fonts, GPU rendering behavior, time zone, and more — to create a unique identifier that remains even in private browsing. Firefox’s new defenses introduce random noise in the rendering of the canvas, restrict system information the browser reveals and attack the most pervasive fingerprinting techniques without compromising site functionality. Mozilla says these protections reduce by about half the percentage of Firefox users that can be uniquely fingerprinted. The protections are active in Private Browsing mode and ETP Strict mode, with expansion to standard browsing planned for future versions.

Private Browsing mode is not saving browsing history, cookies, form data, or cached content after the session is closed. It also applies ETP and fingerprinting protections by default. Firefox does not sell user browsing data and uses end-to-end encryption when syncing user data to Mozilla servers, so Mozilla itself cannot read which sites a user visits.

DNS over HTTPS (DoH) is supported and configurable, sending DNS lookups through an encrypted connection to prevent observation at the network level of which domains a user visits. Firefox supports the HTTPS-Only Mode which forces all connections to be using the HTTPS protocol and warns before loading any page over the http protocol.

TAB MANAGEMENT

Tab Groups, which were introduced in Firefox 137 in April 2025, group tabs into named, color-coded, collapsible collections, which can help users manage many open tabs by keeping related pages together. Firefox 145 introduced thumbnail previews for collapsed groups. Vertical Tabs, also introduced in 2025, shift the tab list to a collapsible left side panel, allowing users to view more tabs simultaneously and freeing up horizontal space for page content.

Link Previews display a thumbnail of a page when you hover over a link, allowing users to choose whether to open the link or not before they commit to opening a new tab.

PRODUCTIVITY FEATURES

The Firefox sidebar offers quick access to bookmarks, history, synced tabs, and an AI assistant panel. The AI panel allows users to connect a third-party chatbot of their choice — including ChatGPT, Gemini or Claude — and interact with it while keeping the current page in view. Conversations go directly between the user and the provider of choice; Mozilla doesn’t have access to them. On-device AI models drive capabilities such as Smart Tab Groups and mobile page summarization without data being sent to external servers.

The built-in PDF viewer opens PDF files in the browser with highlighting, ink drawing, text comments, and a digital signatures feature. A comment sidebar has been added in Firefox 145 that allows users to scan all the annotations and jump between them in long documents.

Firefox Sync, via a free Mozilla account, can sync bookmarks, history, passwords, open tabs, extensions and settings across all devices. Sync data is end-to-end encrypted before leaving the device. The integrated Password Manager saves, generates, and auto-fills passwords and warns users when stored passwords are found in known data breaches. Web apps can be pinned to the Windows taskbar and launched in standalone windows.

On Android, Shake to Summarize creates a summary of the main points on the current page with a shake of the device, with output customized to the type of page — steps for a recipe, scores for a sports article. Reader View removes the navigation and ads from article pages and displays clean, readable text with adjustable font and background. Firefox supports page and PDF translation in dozens of languages, processed locally on the device.

EXTENSIONS

Firefox supports extensions via the Mozilla Add-ons store (addons.mozilla.org). Extensions use the WebExtensions API, which is compatible with the extension API in Chrome, making it easy to port extensions between browsers. The add-ons store has thousands of extensions for ad blocking, privacy, developer tools, productivity, and customization. Unlike Chrome, Firefox has not switched to disabling Manifest V2 extensions in its stable builds, so existing extensions such as uBlock Origin still work without limitations.