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Mozilla is a free, cross-platform Internet software suite, whose components include a web browser and an email client. It is also the name of the open source project responsible for the development of this software.

In February 1998, Netscape released most of the code base for its popular Communicator suite (including the Navigator browser) under an open source license. To support Mozilla's collaborative development, Netscape also created the Mozilla organization and mozilla.org website. Although the original Communicator code was abandoned shortly thereafter, the Mozilla organization eventually succeeded in producing a full-featured Internet suite that surpassed Communicator in both features and stability.

Like many other large software projects, Mozilla itself has become a platform for other programs and libraries written in its domain specific programming[?] environment. Extensions vary widely in complexity, ranging from simple JavaScript-based bookmarklets, to Mozilla feature extensions (such as support for mouse gestures and pie menus), to full-fledged standalone programs. A partial list of programs and extensions for the Mozilla platform can be found on the mozdev.org website.

Table of contents

History of Mozilla

The Netscape Communicator open source release, which came at the height of America's late-1990s economic boom, was greeted by the Internet community with a mixture of acclaim and skepticism. In some circles, Netscape's source release was seen as both a victory for the free software movement and an opportunity for Netscape to tap the power of open source development. This view was particularly popular among users of Linux and other free software. Other observers—including many in the non-open-source business community—interpreted the move as Netscape's surrender in the face of the growing ascendancy of Microsoft's Internet Explorer browser.

Regardless of the public's opinion, development with the Communicator code base proved harder than initially hoped:

  • The Communicator code base was huge and complex.
  • It had to be developed simultaneously on many operating systems, and therefore to cope with their differing libraries and idiosyncrasies.
  • It bore the scars of many rapid cycles of closed-source development on "Internet time". The short development cycles had led programmers to sacrifice modularity and elegance in the scramble to implement more features.
  • Several parts of Communicator's code were never released as open source, due to licensing arrangements with third parties.
As a result, the initial Communicator open source release did not even build cleanly, much less run. This presented steep challenges to the Mozilla core developers (most of whom were still on Netscape's payroll), and even steeper challenges to independent developers wishing to contribute to Mozilla on their own.

Ultimately, the Mozilla core developers concluded that the old code could not be salvaged. They decided to scrap the whole code base and rewrite it from the ground up, which caused one of the lead Netscape developers, Jamie Zawinski to resign. The resulting plan included, among other things, the creation of a whole new cross-platform user interface library and a new HTML rendering engine.

Few observers foresaw the result. The rapid completion of the Gecko HTML layout engine led many to believe that a complete browser could not be far behind. However, producing even a fully functional web browser required much more than a rendering engine; and the Mozilla developers soon envisioned a project more ambitious than a simple web browser. The new Mozilla would be a platform for Internet applications, with a fully programmable user interface and a modular architecture. This Mozilla would function equally well as a host for email clients, instant messaging clients, Usenet news readers, or any number of other applications.

Due to the effort required for this massive rewrite, the project fell far behind its original projected deadlines. In the years that followed, skepticism about Mozilla grew widespread, and some doubted that a finished Mozilla browser would ever see the light of day. However, the project persisted, continuing uninterrupted through both the purchase of Netscape by AOL and the end of the dot-com boom.

By 2002, the Mozilla project had produced a serviceable, standards-based web browser that worked on multiple operating systems, including Linux, Mac OS, Solaris, and Microsoft Windows. The Mozilla 1.0 release was even praised for introducing new features that Internet Explorer lacked, including better support for user privacy preferences and some interface improvements. Additionally, the Mozilla browser became a de facto reference implementation for various World Wide Web Consortium standards, due to its strong support for those standards.

On May 11, 2003, Mozilla 1.4b was released with new features and modifications including:

  • Mozilla on Windows now has support for NTLM authentication. This enables Mozilla to talk to MS web and proxy servers that are configured to use "windows integrated security".
  • Users can now specify "blank page," "home page," or "last page visited" for each of first window, new window and new tab.
  • Users can now specify default font, size and color for HTML mail compose.
  • Image blocking/disabling is now more flexible and users can "view image" to see blocked or not loaded images.
  • Mozilla Mail now has CRAM-MD5 and DIGEST-MD5 AUTH support.
  • "Launch file" after downloading has been enabled for .exe files.
  • As of Mozilla 1.4b, it is possible to build Mozilla for Win32 using GCC. See the win32 build instructions for details.
  • Proxy auto-config (PAC) failover has been implemented.
(From release note[?] in mozilla.org [1] (http://www.mozilla.org/releases/mozilla1.4b/))

Future development of the Mozilla platform

A new development roadmap has been released which marks a change in the future plans for Mozilla. Instead of the current integrated "cross-platform front end" (XPFE) application, Mozilla will become a suite of smaller applications sharing common back-end technology such as the XUL user-interface framework and the Gecko rendering engine. They will continue to work seamlessly with one another, as before, but will be able to integrate better with third-party applications. By cutting the functionality of the suite into pieces, this is intended to improve the project in several ways, by

  • reducing application footprint and code bloat
  • simplifying project management
  • increasing program modularity, and hence reliability and security

This is not a long-term goal: the Firebird (formerly Phoenix) browser is already in an advanced state of development, and the Thunderbird (formerly Minotaur) mail client is in the early stages of being factored out from XPFE.

Mozilla technology


The Mozilla software architecture was, of necessity, fairly modular. As a result, Mozilla development generated several components that have been reused in other contexts. The most prominent of these is the Gecko layout engine, which has been used in other browsers (see Spin-off browsers below).

Also, the task of Mozilla development itself spurred the creation of tools for geographically distributed, cross-platform software development. Some of these tools were widely adopted by the larger open source community, including the following:

Notable features of Mozilla's design

One unique aspect of Mozilla is that the entire user interface, including menus and dialog boxes, is rendered by the Gecko layout engine, rather than by the host operating system's GUI library. This architecture has been controversial. Its defenders cite its flexibility and the fact that it can present a standard GUI across different platforms. Its critics argue that this architecture adversely impacts performance, and that it is a widely-accepted convention of application design to use the native GUI elements of the operating system interface. A number of browsers exist that use the rendering engine only to display the HTML page (see below).

Origins and prophecies: the "Mozilla" name

The Mozilla project takes its name from the cartoon lizard Mozilla, who served as Netscape's mascot in the company's early days. The name is a portmanteau of "Mosaic" (the Netscape browser's predecessor) and "Godzilla" (a movie monster that terrorized Tokyo and other locales). One can surmise that the employees of Netscape hoped to unseat Mosaic as the web's most popular browser. They succeeded---albeit briefly, yielding the position to Internet Explorer soon after. For more on the Mozilla mascot, see the external link for "The Mozilla Museum" (below).

When given the URL about:mozilla, the various versions of the Netscape browser would display a message, in white text on a lurid red background, in the browser window. Version 4 displayed the following prophecy:

And the beast shall come forth surrounded by a roiling cloud of vengeance.
The house of the unbelievers shall be razed and they shall be scorched to the earth. Their tags shall blink until the end of days.
from The Book of Mozilla, 12:10

"Their tags shall blink" refers to the controversial <blink> HTML tag introduced in an earlier Netscape version. This proprietary HTML extension, which made text blink on and off, was widely derided as annoying, distracting, and ugly. Soon after its introduction, the blink tag joined hideously garish backgrounds and animated GIFs as metonymy for badly designed web pages.

Later Netscape browser versions (as well as the Mozilla browser itself), which were actually based on the Mozilla code, displayed the following:

And the beast shall be made legion. Its numbers shall be increased a thousand thousand fold. The din of a million keyboards like unto a great storm shall cover the earth, and the followers of Mammon shall tremble.
from The Book of Mozilla, 3:31
(Red Letter Edition)

This text probably referred to Netscape's hope that, by opening the Mozilla source, they could attract a "legion" of developers who would help improve the software. Some suggested that "Mammon" referred obliquely to Microsoft, which seemed plausible given that Microsoft's Internet Explorer was Mozilla's chief competition.

Version History

Early versions of Mozilla were slow and buggy. Mozilla became about as stable as Netscape 4.7x only from 0.9.2 or 0.9.3 builds onwards. From 0.9.5 (October 12, 2001) onwards the releases have been fast and reliable, largely due to the implementation of formal code review techniques by the Mozilla project managers.

VersionRelease dateMost important changes
Milestone 1?Conversion to the "raptor" codebase; about 100 bugfixes
Milestone 2January 31, 1999Platform parity (Windows / Linux / MacOS); about 85 bugfixes
Milestone 3March 19, 1999 
Milestone 4April 15, 1999 
Milestone 5May 5, 1999 
Milestone 6May 29, 1999 
Milestone 7June 22, 1999 
Milestone 8July 16, 1999 
Milestone 9August 26, 1999 
Milestone 10October 8, 1999 
Milestone 11November 16, 1999 
Milestone 12December 21, 1999 
Milestone 13January 26, 2000 
Milestone 14March 1, 2000 
Milestone 15April 18, 2000 
Milestone 16June 13, 2000Autocomplete, Chatzilla, HTTP/1.1 support, skin support, full session history support
Milestone 17August 7, 2000Classic theme, alpha transparency, MNG support, plugin support on Linux
Milestone 18October 12, 2000Java support on Linux, Modern theme
Mozilla 0.6December 6, 2000source-only release of the base for Netscape 6.0
Mozilla 0.7January 9, 2001Personal security manager; SSL and mousewheel support on MacOS; forced reloads from server
Mozilla 0.8February 14, 2001Find and replace; first introduction of pop-up blocking; improved bookmark manager
Mozilla 0.8.1March 26, 2001Improved Chatzilla and Javascript Console; initial gopher support
Mozilla 0.9May 7, 2001Automatic proxy configuration; personal security manager 2.0; performance improvements
Mozilla 0.9.1June 7, 200134 crasher bugs fixed; overhauled Modern theme; XSLT support; bidi support for Hebrew and Arabic
Mozilla 0.9.2June 28, 200125 crasher bugs fixed; Quick Launch (preloading to reduce startup times) implemented on Windows
Mozilla 0.9.3August 2, 2001More stability work (Mozilla is now considered more stable than Netscape 4.78)
Mozilla 8, 2001source-only release of the base for Netscape 6.1
Mozilla 0.9.4September 14, 2001Quick Launch enabled by default; Arabic language support on Linux
Mozilla 0.9.5October 12, 2001Tabbed Browsing; SOCKS support for almost all protocols; ECMAScript debugger Venkman (http://www.mozilla.org/projects/venkman/venkman-walkthrough)
Mozilla 0.9.6November 20, 2001Page icons displayed in toolbar (except for favicons); print preview; BMP and ICO support on all platforms
Mozilla 31, 2001source-only release of the base for Netscape 6.2
Mozilla 0.9.7December 21, 2001Favicon support.
Mozilla 0.9.8February 4, 2002Hebrew support on Solaris; Hebrew and Arabic support on MacOS; Document Object Model inspector
Mozilla 0.9.9March 11, 2002a new mail notification sign that appears in the Windows System tray.
Mozilla 1.0 RC1April 18, 2002Viewing source of cgi generated pages works, reorganized menus, new Download Manager
Mozilla 1.0 RC2May 10, 2002 
Mozilla 1.0 RC3May 23, 2002139 bug fixes since RC2.
Mozilla 1.0June 5, 2002first 'official' release
Mozilla 1.1August 26, 2002performance, stability, compatibility and standards conformance improved
Mozilla 1.0.1September 10, 2002over 650 bugfixes to 1.0.
Mozilla 1.2November 26, 2002type ahead find, improved keyboard access, link prefetching
Mozilla 1.2.1December 2, 2002released to correct a DHTML bug found in Mozilla 1.2
Mozilla 1.0.2January 7, 2003stability and security improvements and fixes for standards support
Mozilla 1.3March 13, 2003basic junk mail classification capabilities and image auto sizing
Mozilla 1.3.1May 7, 2003released to restore XPI functionality on Mac OS X
Mozilla 1.4bMay 7, 2003 
Mozilla 1.4 RC1May 29, 2003more junk mail controls, smooth scrolling, bookmarks overhaul, streamlined pop-up blocking
Mozilla 1.4 RC2June 17, 2003Lots of bug fixes.
Mozilla 1.4 RC3June 24, 2003More bug fixes.
Mozilla 1.4June 30, 2003Official 1.4 release.

Early reviews of Mozilla 1.0 were favorable, describing Mozilla as fast and stable, and praising new features such as tabbed browsing and pop-up blocking.

One advanced setting which is highly beneficial to users of Mozilla is the ability to use the pipelining feature of HTTP 1.1, which results in much faster download times for sites with multiple images.

Spin-off Browsers

Browsers that use the Gecko layout engine for the entire user interface:

Browsers that just use the Gecko layout engine for webpage display only:

External links

All Wikipedia text is available under the terms of the GNU Free Documentation License

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