Firefox in a Nutshell

Introduction to Firefox

Our guess is that you wouldn't be reading this chapter unless you already knew what a Web browser was. However, if you don't know, a browser is the software you use to visit and view Web sites on the Internet.

The Internet is a giant network of computers, all connected to each other. Some of the computers are "Web servers" – computers that have Web sites on them. If you want to visit these sites from your computer or a mobile device, you need a way to surf around and display them. That's what a browser does.

One of the most popular browsers is Firefox, a free, open source Web browser created by the Mozilla foundation in 2003. Firefox runs on all the major operating systems – Windows, MacOS and Linux – and it has been translated into more than 75 languages. Best of all, It's completely free of charge. 

Where to get Firefox

If you want to install Firefox you can find the installation files here:

When you visit this site you will be presented automatically with the correct installation file for your operating system (Windows/Mac/Linux). For more information on how to install Firefox on each of these operating systems, please see later chapters. 

What is a Firefox Add-on?

When you first download and install Firefox, it can handle basic browser tasks immediately. You can also add extra capabilities or change the way Firefox behaves by installing add-ons, small additions that extend Firefox's power. There are several kinds of add-ons:

  • extensions that provide additional functionality to the browser
  • themes that change Firefox's appearance
  • plugins that help Firefox handle things it normally can't process (for instance Flash movies, Java applications, and so on).

The variety of add-ons available is enormous. You can add dictionaries for different languages, track the weather in other countries, get suggestions for Web sites which are similar to the one you are currently viewing, and much more. Firefox keeps a list of current add-ons on its site (

Before you install any add-on, keep in mind that it can read a lot of information from your browser so it is very important to choose add-ons from trusted sources. Otherwise, an add-on you install might share information about you without your knowing, keep a record of the sites you have visited, or even harm your computer.

We recommend that you never install an add-on for Firefox unless it is available from the Firefox add-on pages. You should also never install Firefox unless you get the installation files from a trusted source. It is important to note that using Firefox on someone else's computer or in an Internet café increases your potential vulnerability.

About this Manual

This summary of the Firefox manual focusing on the security use was commissioned by Internews as part of the Human Rights Connect Expand programme. 

It contains an updated summary of the longer Firefox manual on FLOSS Manuals and uses other existing material from Bypassing Internet Censorship and Basic Internet Security. New original material has been added by project editors Mick Fuzz and Jacques Sauvage. 

Original Firefox BookSprint

The longer Firefox manual evolved during a two-day Book Sprint at the Doctrain West conference. Scott Abel extended the invitation, and the sprint was a collaborative effort by FLOSS Manuals, Doctrain West, and the Mozilla Foundation. 25 writers collaborated over two days in virtual and real space to produce a book in two days! In addition to original content, large amounts of material were reused from the excellent Firefox Support Knowledge Base.


What is FLOSS?

Firefox is entirely free (FLOSS) software. You do not have to pay anything to download and install it. 

FLOSS is an abbreviation for Free/Libre/Open Source Software. While there are dozens of variations of these terms in use, all FLOSS software shares some of the same basic ideals of software freedom, including:

  • Freedom to run the program
  • Free access to complete source code
  • Freedom to study the code
  • Freedom to modify the code
  • Freedom to redistribute the modified code

Firefox and the Community

For many users, Firefox is their first introduction to FLOSS and the ideas it represents. FLOSS is a core aspect of the Mozilla project, which has developed the Firefox web browser. As a result, everyone is free to use, copy, improve, or extend Firefox. Another core aspect of the Mozilla project is its participatory development strategy, which means anyone can get involved with making Firefox better. Millions of community members help make Firefox better every day.

More than 30% of Mozilla code is contributed by volunteers, with the rest being contributed by full-time contributors who are paid either by Mozilla or by other companies involved in Mozilla development. Mozilla is a diverse set of people, and nearly anyone can make a big difference, whether by developing code, writing documentation, testing software, or just telling friends about Firefox!