Pale Moon is a web browser

Web browser

A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...

 based on Mozilla Firefox

Mozilla Firefox

Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. , Firefox is the second most widely used browser, with approximately 25% of worldwide usage share of web browsers...

. It uses the Mozilla back-end (powered by Mozilla). It is available for Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 platforms and distributed by Moonchild (M.Straver). Pale Moon builds

Software build

In the field of computer software, the term software build refers either to the process of converting source code files into standalone software artifact that can be run on a computer, or the result of doing so...

 on Firefox, optimizing for efficiency of code and aimed at current and modern microprocessor

Microprocessor

A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...

s. Pale Moon is freely downloadable with open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 code and proprietary

Proprietary software

Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...

 freeware binaries. Most of the available Firefox extensions

Extension (Mozilla)

]Add-ons are installable enhancements to the Mozilla Foundation's projects, and projects based on them. Add-ons allow the user to add or augment application features, use themes to their liking, and handle new types of content.-Extensions:...

 and plugins are compatible with Pale Moon.

Optimization

Pale Moon is optimized using the following methods:

Binary code optimization

• Compiled with a high level of compiler optimization
  Compiler optimization
  Compiler optimization is the process of tuning the output of a compiler to minimize or maximize some attributes of an executable computer program. The most common requirement is to minimize the time taken to execute a program; a less common one is to minimize the amount of memory occupied...
  
  :
  • Pale Moon is compiled with either -O2 or -Ox, both optimization flags of the Microsoft C compiler to get maximum speed.
  • Pale Moon is compiled to use the SSE2
    SSE2
    SSE2, Streaming SIMD Extensions 2, is one of the Intel SIMD processor supplementary instruction sets first introduced by Intel with the initial version of the Pentium 4 in 2001. It extends the earlier SSE instruction set, and is intended to fully supplant MMX. Intel extended SSE2 to create SSE3...
    
     processor instruction set, greatly increasing speed and efficiency of some operations.

The resulting browser will not run on particularly old hardware as a result, but by cutting out support for older systems, Pale Moon works with an optimized code base that takes full advantage of modern processor instruction sets.

Removing functions that are not in high demand

• Pale Moon removes a few features that are not in high demand, but are integral in Firefox:
  • Accessibility features
  • Parental controls
    Parental controls
    Parental controls are features which may be included in digital television services, computer and video games, mobile phones and computer software...
    
    
  • Crash reporter
    Crash reporter
    A crash reporter is an application whose function is to report crash data to a third party, usually to the party responsible for the crashed program. Crash reports often include data such as stack traces, type of crash, and version of software...
    
    
  • ActiveX
    ActiveX
    ActiveX is a framework for defining reusable software components in a programming language-independent way. Software applications can then be composed from one or more of these components in order to provide their functionality....
    
     and ActiveX scripting
    Active Scripting
    Active Scripting is the technology used in Windows to implement component-based scripting support. It is based on COM and allows installation of additional scripting engines in the form of COM modules.-Uses and history:The Active Scripting technologies were first released in 1996, with the...
    
    

Speed comparisons

The resulting differences in speed by using optimizations and also removing certain program features like accessibility and parental controls have shown a significant advantage of the optimized browser compared to Firefox, even though the source code is otherwise mostly untouched.

Interface changes

Pale Moon, since v4, has also made some changes to the program's interface (layout) compared to its sibling Firefox:

• Pale Moon retains a status bar
• Navigation controls are grouped together
• Tabs by default are not placed on top

Downloads available

Pale Moon offers a number of different downloads:

• Version 3.x (Based on Firefox 3.x, supports processors that only support SSE
  SSE
  -Computing:*Server-sent events, a technology to push content to web clients*Simple Sharing Extensions, a specification that extends RSS from unidirectional to bidirectional information flows*SPARQL Syntax Expressions*Microsoft SQL Server Express Edition...
  
  )
  • Desktop (32-bit)
  • Portable (32-bit)
• Version 8.x (based on Firefox 8.x)
  • Desktop (32-bit and 64-bit)
  • Portable (32-bit and 64-bit)
• The source code for the browser
• Archived older versions

License

The same as Firefox, the Pale Moon source code is open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

, with the source code residing under the MPL 1.1

Mozilla Public License

The Mozilla Public License is a free and open source software license. Version 1.0 was developed by Mitchell Baker when she worked as a lawyer at Netscape Communications Corporation and version 1.1 at the Mozilla Foundation...

 except for parts relating to branding.
Unlike Firefox, the Pale Moon binaries have a redistribution license which allows redistribution but only under certain conditions. According to the author, this is to prevent the possibility of any confusion with tainted versions (see the Firefox branding argument Mozilla Firefox#Trademark and logo). The name Pale Moon (relating to the browser), the Pale Moon logo and other proprietary artwork are the intellectual property of M. Straver, and accordingly cannot be used on other third party Firefox builds or other related products without his permission.