Firefox is available as a free download. All Mozilla software is licensed under the Mozilla Public License. Instructions on how to obtain the source code can be found here.

An enormous number of add-ons.

With new integrations focused on security and performance, Firefox is faster and less likely to have problems during use than ever before.

Blocks tracking cookies, finger print scanners and Cryptominers by default. Can be changed to the user's individual needs.

Beyond the toolbar and tabs, it darkens UI elements such as the URL-bar, pop-downs, new-tab page and more.

Mozilla is one of the first browsers that advocates privacy. They believe that internet should be in the user's control and not those who run the websites, and so they give tools inside the browser to make the user be more in control.

The Mozilla Manifesto outlines the company's mission and principles. Paraphrasing, they want the Internet to be a free and open resource, and to enable individuals to get the best use of that resource. They do this by creating open source software to which anyone may contribute, so long as such contributions fit with their principles (both ethical and technical).

Firefox Sync is an optional feature in Firefox that allows syncing bookmarks, passwords, and add-ons between devices.

Great library of add-ons.

Unlike other browsers, Mozilla uses almost the same codebase as with the desktop version so extensions work as-is without code modifications - something other browsers cannot do due to their breaking and sometimes unrelated code branches to the mainline desktop branch.

The Firefox Quantum update (FF57) greatly increases the render speed and general performance of the browser, by taking better advantage of the user's hardware.

Firefox uses its own rendering engine (called Gecko), instead of Google-controlled Blink like the vast majority of other browsers.

Master about:config and uBlock Origin, and all Firefox-based browsers will be yours.

Firefox 57 (Quantum) and newer uses less resources than ever. It is proven with benchmark done by AppleInsider.

Firefox scores strongly on HTML5 feature support
Though not as strongly as Chromium/Chrome browsers do.

Firefox is automatically updated on the platforms where it makes sense.

Firefox has a solid mobile app.

Reader View in Firefox allows users to read an article without any distractions by removing ads, unrelated elements and other distractive objects (similar to Microsoft Edge's Reading Mode and Safari's reader mode).

Firefox used to be a trailer in memory usage, but as of 2017 it's less hungry for memory than competitors like Edge, Chrome, Safari and Opera.

The built-in developer tools have been merged with the popular FireBug extension since FF57.

Firefox is one of the few browsers that you can tag your bookmarks. You can view a list of tags and can search your bookmarks in the address bar with tags.

Reader View in Firefox allows users to read an article without any distractions by removing ads, unrelated elements and other distractive objects (similar to Microsoft Edge's Reading Mode and Safari's reader mode).

Within the browser itself, you can easily take screenshots and save them to your computer.

Helps store your usernames and passwords. Lockwise also lets you know if any of the sites you have login details for have had their (and potentially your) data leaked!

Font rasterizing on Windows is much better than in competitors. Even smaller text is clear and contrast.

FF experiments are Mozilla projects available from FF Test Pilot, such as Firefox Colour, witch lets you customise your browser theme to your liking!

The only web browser that only preloads entire HTML5 video which is useful for slow internet.

Firefox and the entire Mozilla team are openly against the addition to Google's proposed Web Environment Integrity API.

Many Linux distributions come preinstalled with Mozilla Firefox.

In order to add an open page to the bookmark bar, the tab can be dragged down and is added immediately.

Firefox Reader Mode includes Narrate, a feature that adds text-to-speech functionality to the browser.

Helps store your usernames and passwords. Lockwise also lets you know if any of the sites you have login details for have had their (and potentially your) data leaked!

The newer versions of it will soon use WebRender to render webpages, which'll make it much more efficient by utilizing GPU to paint webpages.

Firefox comes with built-in Pocket integration that can allow users to quickly save the article for a read it later function to easily find any articles saved in Pocket from various sources and devices.