Overview

Mozilla Firefox is a free, open-source web browser developed by Mozilla. It lets users visit websites, use online applications, watch videos, manage downloads and organize research in a customizable interface. Available on Windows, macOS, Linux, Android, iPhone and iPad, it is designed for everyday browsing as well as professional use and web development.

Firefox is distinguished in particular by its Gecko rendering engine, used on desktop and Android. This technical foundation is independent of Chromium, the engine underlying many competing browsers. On iPhone and iPad, the Firefox app retains Mozilla's interface and services but uses WebKit to display pages; its capabilities are therefore not exactly the same as those of the desktop version.

Privacy protection is one of its main priorities. The browser automatically blocks many known trackers and isolates cookies to limit tracking between sites. It also offers private browsing, advanced protection settings and controls over transmitted data. These features reduce certain forms of tracking, but they do not make browsing anonymous or prevent a website from collecting information that a user chooses to provide.

Firefox also emphasizes control over its interface: vertical tabs, tab groups, a sidebar, themes and extensions let users adapt the browser to different workflows. An optional Mozilla account adds synchronization of bookmarks, passwords and tabs between devices, while several features, such as page translation, can run directly on the user's device.

The browser is free, with no Premium edition required to access its main features. Mozilla also finances its activities through search partnerships and sponsored placements or suggestions, which users can configure or disable. Certain separate Mozilla services may be paid; these should not be confused with the price of Firefox itself.

As of September 19, 2026, the stable desktop version is Firefox 156, released on September 15. Mozilla switched to a two-week release cycle starting with Firefox 155. Firefox ESR, meanwhile, follows an extended update policy intended notably for organizations and environments that favor less frequent deployments.

Features

Browsing, search and tab organization

Firefox brings together the functions expected of a modern browser: a combined address and search bar, bookmark management, history, downloads, video playback and support for web standards. It can import favorites, passwords and history from other browsers to make migration easier.

Organizing open pages has become increasingly important. Tab groups bring several pages together around a project, topic or task; vertical tabs improve title readability when many pages remain open. A customizable sidebar gives access to bookmarks, history and synchronized tabs without replacing the current page.

Pinned tabs keep frequently used services one click away. Picture-in-Picture lets users detach certain videos into a small window while browsing other pages. Together, these tools make Firefox an adaptable workspace, although they do not turn it into a complete project manager.

Enhanced Tracking Protection

Enhanced Tracking Protection is enabled by default. It restricts known trackers, certain tracking scripts and other data collection techniques depending on the selected protection level. Total Cookie Protection isolates cookies by website to limit their use for tracking someone across domains.

Users can keep Standard mode, enable Strict mode or customize which categories to block. The shield near the address bar indicates which protections are applied to the current site; exceptions can be added when a service no longer works correctly.

Firefox also provides options such as DNS over HTTPS, control over permissions granted to websites and protection against certain fingerprinting techniques. These mechanisms complement protections against deceptive pages or dangerous downloads without guaranteeing absolute security: updates and vigilance against fraudulent sites remain essential.

Private browsing and data settings

Private browsing creates a session whose browsing history and cookies are not retained in the same way as a normal session after the private windows are closed. It is useful for temporarily separating research or avoiding leaving certain traces in the usual profile.

This mode is neither a VPN nor an anonymity tool. Visited websites, an employer, a network or an internet service provider may still have information about the connection. Likewise, Enhanced Tracking Protection does not prohibit all advertising and does not replace consent or necessary checks when voluntarily providing data to a service.

Mozilla documents the technical, interaction and search data that may be processed to provide the browser and its services. Settings notably allow users to manage certain data collection, search suggestions, sponsored content and site permissions. Available choices depend on the platform and feature concerned.

Extensions, themes and customization

The Firefox Add-ons catalog lets users install extensions to expand the browser: content blocking, password management, note-taking, screenshots, accessibility or developer tools. Themes, meanwhile, change the interface's appearance. Add-ons are developed by Mozilla or third-party publishers, with their own updates and permissions.

Extensions are particularly important on desktop, where they can turn Firefox into an environment adapted to a profession or specific use. Firefox for Android also supports compatible extensions, available through its manager or dedicated catalog. By contrast, Firefox extensions for desktop and Android cannot be installed in Firefox on iPhone and iPad.

An extension may access visited pages or other data depending on the permissions it requests. It is therefore preferable to check its publisher, permissions and maintenance before installing it, rather than accumulating add-ons that slow browsing or multiply access to data.

Synchronization with a Mozilla account

A free Mozilla account lets users synchronize bookmarks, usernames and passwords, history and tabs across multiple Firefox installations. Someone can begin research on a computer, recover their open pages on mobile or send a tab from one device to another.

Synchronization uses encryption to protect the relevant data. Users can choose which categories to synchronize, and creating an account is not necessary to use Firefox locally. Exact features and available settings may vary by version and device.

Synchronization does not, however, replace every form of backup. For a major migration or a profile containing data that would be difficult to reconstruct, exporting bookmarks and backing up the profile remain useful precautions.

Reading, on-device translation and PDF documents

Reader View simplifies compatible pages to prioritize text and reduce elements that may interfere with reading. Firefox also has built-in translation: the required models are downloaded to the device and the text of supported pages is translated locally, without being sent to an external translation server. Availability depends on the supported languages and features.

The built-in PDF viewer does more than display files. It notably allows users to add text, draw, highlight, comment and insert a signature or image into compatible documents. A modified file can then be saved. This is suitable for annotations and simple forms, but it does not replace a specialized tool when a PDF needs extensive restructuring or changes to its original text.

Version 156 notably improves PDF viewer startup. For users who consult many articles, documentation pages and attachments, this combination reduces the need to switch applications systematically.

Optional AI features

Firefox offers features related to artificial intelligence, including on-device translation, certain link previews, tab grouping suggestions and access to chatbots from the sidebar. It is important to distinguish features running locally from those that call third-party services: opening an external chatbot involves that provider's terms and practices.

Since Firefox 148, an AI Controls section has allowed users to manage features individually or block the browser's proposed AI enhancements. Using these features is therefore not mandatory in order to continue browsing. Their availability and behavior may change with versions and devices.

This approach allows users to retain a traditional experience, enable only useful functions or use separate AI services when needed. It does not mean that every AI feature on the Web becomes local or confidential simply because it is opened in Firefox.

Web developer tools

Firefox includes developer tools for inspecting HTML and CSS styles, examining JavaScript, debugging scripts, monitoring network requests and analyzing certain performance characteristics. Responsive Design Mode helps test different screen dimensions, while accessibility and storage tools make it easier to examine a web application.

The Gecko engine, distinct from Chromium on desktop and Android, offers an additional benefit for developers: testing a site in Firefox checks compatibility with another implementation of web standards rather than assuming that a correct result in a Chromium browser applies everywhere.

The tools evolve alongside the browser. Firefox 156 notably improves certain information displayed in the Inspector, but development environments still need to be tested on the browsers and devices actually targeted by a project.

Mobile versions and Firefox ESR

On Android, Firefox provides a touch-friendly browser with tracking protection, synchronization and compatible extensions. On iPhone and iPad, it provides the Mozilla experience and synchronization but relies on WebKit rather than Gecko and does not include the desktop extension catalog.

For businesses and organizations, Firefox ESR (Extended Support Release) follows a slower pace of functional change while receiving security fixes. Administrative policies allow the browser to be configured and deployed across a fleet of computers. It is not a paid edition or separate subscription, but a release channel suited to different maintenance requirements.

The Beta, Developer Edition and Nightly channels serve other purposes: exploring upcoming features or testing changes before their general release. They may be less suitable for everyday use that requires the stability of the standard channel.

Use cases

Browsing every day while limiting tracking

Firefox is suitable for visiting websites, completing online procedures, shopping, searching and watching videos. Enhanced Tracking Protection and cookie controls reduce certain forms of tracking without requiring complex configuration immediately after installation.

Users can then adjust privacy settings to suit their needs. When a website refuses to load or a video player malfunctions, the protection exception provided for that domain can help find a compromise without systematically disabling protections everywhere.

Organizing documentary research

Tab groups, bookmarks and sidebar features make it possible to separate several topics, keep important pages and quickly retrieve a reference. Reader View makes long texts easier to read, while PDF annotation avoids opening another application simply to add a comment or fill out a basic form.

With synchronization, research started on a computer can continue on a phone or tablet. Firefox then serves as an organized point of access to web resources without claiming to replace a knowledge manager or specialized document library.

Testing and developing a website

Developers can inspect page elements, analyze requests, examine JavaScript errors and test responsive layouts directly through the built-in tools. Checking a website in Firefox complements testing performed in Chromium-based browsers.

Specialized extensions and development editions can enrich this workflow, while stable versions remain relevant for checking the actual experience of visitors.

Using the same browser across devices

A Mozilla account connects Firefox installations so bookmarks, passwords and open tabs can be retrieved. This is practical when switching from a Linux or Windows workstation to a smartphone, or recovering a page viewed on a family computer.

Users simply need to bear in mind that the interface and extensions are not identical on every platform, particularly on iOS and iPadOS.

Conclusion

Mozilla Firefox is a free, open-source general-purpose browser combining everyday browsing, productivity tools, tracking protection and customization. Its appeal does not rest on a single feature: it comes from the ability to organize browsing while retaining control over many browser settings.

Using Gecko on desktop and Android also represents an important technical distinction on a Web where many browsers use Chromium. For users, this independence provides another implementation of the web engine; for developers, it encourages compatibility checks beyond a single browser family.

Tab groups, the sidebar, extensions and synchronization can make Firefox particularly practical when the browser is used throughout the day for work, learning or research. On-device translation and PDF annotations complement these activities without immediately requiring external services.

It is nevertheless essential to distinguish privacy protection from anonymity. Firefox blocks many known tracking mechanisms but does not automatically conceal the identity of someone who signs into an account, nor all the information visible on a network. The browser also collects certain technical data and offers configurable sponsored placements, as documented in its privacy policy.

Its variants also require a few clarifications: the iOS version does not use Gecko, extensions differ by device, and Firefox ESR targets a more conservative deployment approach than the standard release channel. AI features remain optional, and some depend on third-party services rather than local execution.

For browsing, organizing research, consulting documents, customizing a browser or testing websites on an engine independent of Chromium, Firefox offers a complete environment without a mandatory subscription for its main features.

Points to consider

  • Firefox is free and open source, but certain associated Mozilla services may be paid. Its code is primarily under MPL 2.0; its name and logo are subject to separate trademark rules.
  • Tracking protection does not guarantee anonymity. Private browsing removes certain local traces after the session but does not automatically conceal activity from websites or networks.
  • Sponsored suggestions and content may appear, notably in the address bar or new tab depending on the country. They can be configured and disabled.
  • Firefox uses Gecko on desktop and Android but WebKit on iPhone and iPad. Technical capabilities and the interface are therefore not perfectly identical.
  • Extensions available on desktop or Android cannot be installed unchanged on iOS/iPadOS. Check add-on compatibility before building a workflow that depends on them.
  • Strict tracker blocking can disrupt certain websites. A targeted exception is preferable to disabling protections globally when a legitimate service malfunctions.
  • Synchronization is optional and requires a Mozilla account. It makes moving between devices easier but does not necessarily replace an independent profile backup.
  • Built-in translations can run locally, whereas third-party chatbots accessed through Firefox apply their own data processing terms.
  • Firefox ESR has its own update schedule. It should be distinguished from the standard stable version, which moved to releases every two weeks in September 2026.