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Download Firefox 39.0

Mozilla Firefox for PC Windows 39.0

By Mozilla Organization  (Open Source)
User Rating

Managing Browser Add-Ons In Mozilla Firefox

Mozilla Firefox is a fast, light and tidy open source web browser. At its public launch in 2004 Mozilla Firefox was the first browser to challenge Microsoft Internet Explorer’s dominance. Since then, Mozilla Firefox has consistently featured in the top 3 most popular browsers globally. The key features that have made Mozilla Firefox so popular are the simple and effective UI, browser speed and strong security capabilities. The browser is particularly popular with developers thanks to its open source development and active community of advanced users.

Easier Browsing

Mozilla put of a lot of resources into creating a simple but effective UI aimed at making browsing quicker and easier. They created the tab structure that has been adopted by most other browsers. In recent years Mozilla has also focused on maximizing browsing area by simplifying toolbar controls to just a Mozilla Firefox button (which contains settings and options) and back/forward buttons. The URL box features direct Google searching as well as an auto predict/history feature called Awesome Bar. On the right side of the URL box there are bookmarking, history and refresh buttons. To the right of the URL box is a search box which allows you to customize your search engine options. Outside of that a view button controls what you see below the URL. Next to that you have the download history and home buttons.


Mozilla Firefox boasts impressive page load speeds thanks to the excellent JagerMonkey JavaScript engine. Start up speed and graphics rendering are also among the quickest in the market. Mozilla Firefox manages complex video and web content using layer-based Direct2D and Driect3D graphics systems. Crash protection ensures only the plugin causing the issue stops working, not the rest of the content being browsed. Reloading the page restarts any affected plugins. The tab system and Awesome Bar have been streamlined to launch/get results very quickly too.


Mozilla Firefox was the first browser to introduce a private browsing feature which allows you to use the internet more anonymously and securely. History, searches, passwords, downloads, cookies and cached content are all removed on shutdown. Minimizing the chances of another user stealing your identity or finding confidential information. Content security, anti-phishing technology and antivirus/antimalware integration ensures your browsing experience is as safe as possible.

Personalisation & Development

One of the best features of the Mozilla Firefox UI is customization. Simply right click on the navigation toolbar to customize individual components or just drag and drop items you want to move around. The inbuilt Mozilla Firefox Add-ons Manager allows you to discover and install add-ons within the browser as well as view ratings, recommendations and descriptions. Read more about the top recommended add-ons for Mozilla Firefox. Thousands of customizable themes allow you to customize the look and feel of your browser. Site authors and developers can create advanced content and applications using Mozilla’s open source platform and enhanced API.

Looking for the Mac version of Mozilla Firefox? Download Here

Looking for the 64-bit version of Mozilla Firefox? Download Here

Check out our guide to alternative browsers if you're looking for something a little different.

Please note: from version 53.0 onward Windows XP and Vista are no longer supported.

Title: Firefox 39.0
Filename: Firefox Setup 39.0.exe
File size: 39.22MB (41,128,904 bytes)
Requirements: Windows 2000 / XP / Vista / Windows 7 / XP 64-bit / Vista 64-bit / Windows 7 64-bit / Windows 8 / Windows 8 64-bit / Windows 10 / Windows 10 64-bit
Languages: Multiple languages
License: Open Source
Date added: July 3, 2015
Author: Mozilla Organization
MD5 Checksum: 3D6E1F120E618AB6EE653DBA79BDE8C6

# New
- Share Hello URLs with social networks
- Project Silk: Smoother animation and scrolling (Mac OS X)
- Support for 'switch' role in ARIA 1.1 (web accessibility)
- SafeBrowsing malware detection lookups enabled for downloads (Mac OS X and Linux)
- Support for new Unicode 8.0 skin tone emoji
# Changed
- Removed support for insecure SSLv3 for network communications
- Disable use of RC4 except for temporarily whitelisted hosts
- The malware detection service for downloads now covers common Mac file types (Bug 1138721)
- Performance of displaying dashed lines is improved (Mac OS X) (Bug 1123019)
- List-style-type now accepts a string value
- Enable the Fetch API for network requests from dedicated, shared and service workers
- Cascading of CSS transitions and animations now matches the current spec
- Implement <link rel="preconnect">allowing anticipation of a future connection without revealing any information
- Added support for CSS Scroll Snap Points
# Developer
- Drag and drop enabled for nodes in Inspector markup view
- Webconsole input history persists even after closing the toolbox
- Cubic bezier tooltip now shows a gallery of timing-function presets for use with CSS animations
- localhost is now available offline for WebSocket connections
# Fixed
- Improve performance for IPv6 fallback to IPv4
- Fix incomplete downloads being marked as complete by detecting broken HTTP1.1 transfers
- The Security state indicator on a page now correctly ignores loads caused by previous pages
- Fixed an issue where a Hello conversation window would sometimes fail to open
- A regression that could lead to Flash not displaying has been fixed
- Update to NSS 3.19.2
- Various security fixes