In celebration of the 10th anniversary of Firefox, we unveiled Firefox Developer Edition, the first browser created specifically for developers. At that time, we also announced plans to ship a 64-bit version of Firefox. Today we’re happy to announce the next phase of that plan: 64-bit builds for Firefox Developer Edition are now available on Windows, adding to the already supported platforms of OS X and Linux.

A 64-bit build is a major step toward giving users rich, desktop-quality app experiences in the browser. Let’s also take a look at at some of the other features that make this a release worth noting. If you haven’t downloaded the Developer Edition browser yet, it’s a fine time to give it a try. Here’s why:





Unreal demo in Win 64-bit Developer Edition

Run larger applications

A 32-bit browser is limited to 4GB of address space. That address space is further whittled down by fragmentation issues. Meanwhile, web applications are getting bigger and bigger. Browser-based games that deliver performant, native-like gameplay, such as those built with Epic Games’ Unreal Engine, are often much larger than we expect from traditional web applications. These games ship with large assets that must be stored in memory so they can be synchronously loaded.

For some of the largest of these apps, a 64-bit browser means the difference between whether or not a game will run. For example, when porting to asm.js it’s recommended to keep heap size to 512mb in a 32-bit browser. That goes up to 2GB in a 64-bit version of Firefox.

Emscripten helps port C and C++ code to run on the Web and deliver native-like performance. For an in-depth look at how assets are stored and accessed using a variety of methods in asm.js/emscripten built applications, read Alon Zakai’s post on Synchronous Execution and Filesystem Access in Emscripten.

Gain faster execution and increased security

64-bit Firefox just goes faster. We get access to new hardware registers and instructions to speed up JavaScript code.

For asm.js code, the increased address space also lets us use hardware memory protection to safely remove bounds checks from asm.js heap accesses. The gains are pretty dramatic: 8%-17% on the asmjs-apps-*-throughput tests as reported on arewefastyet.com.

The larger 64-bit address space also improves the effectiveness of ASLR (address space layout randomization), making it more difficult for web content to exploit the browser.

Firefox Developer Edition additions and improvements

Beyond the new 64-bit capabilities, the Firefox 38 Developer Edition release implements many new features, as it does every 6 weeks when it is updated. Some of these are described below. For all the details and associated bugs in progress, you’ll want to visit the release notes.

WebRTC changes

In a post about WebRTC from 2013, we documented some workarounds and limitations of WebRTC mozRTCPeerConnection. One fix involved adding multiple MediaStreams to one mozRTCPeerConnection and renegotiating on an existing session.

The new version of Firefox Developer Edition fixes these issues. We now support adding multiple media streams (camera, screen sharing, audio stream) to the same mozRTCPeerConnection within a WebRTC conversation. This allows the developer to call the addStream method for each additional stream, which in turn triggers the onAddStream event for the clients.

Renegotiation allows streams to be modified during a conversation, for example sharing a screen stream during a conversation. This is now possible without re-creating a session.





WebRTC with multiple streams

Last week we announced that WebRTC requires Perfect Forward Secrecy (PFS) starting in Firefox 38. We’ll dig a little deeper into details of our WebRTC implementation in an upcoming article. Stay tuned.

The BroadcastChannel API

The BroadcastChannel API allows simple messaging between browser contexts with the same user agent and origin is now available. Here’s more detail and some ideas for how to use the BroadcastChannel API in Firefox 38.

Support for KeyboardEvent.code

KeyboardEvent.code is now enabled by default. The code attribute give a developer the ability to determine which physical key is pressed without keyboard layout or keyboard state modifications.





KeyboardEvent code attribute

For more examples of uses cases see the motivation section of the UI Events Specification (formerly DOM Level 3 Events).

XHR logging

The Network Monitor already displays a great deal of information on XMLHttpRequests, but often the console is used to debug code along with network requests. In the latest Developer Edition of Firefox, the console now supports filtering XMLHttpRequests within console logging.





Network Monitor XHR Request





XHR logging in console

Let us know what you think

Many additional improvements are available in this version. Download it now. Tell a friend.

As always, you can take a close look at the Developer Edition release notes. Please be sure to share your feedback and feature ideas in the Firefox Developer Tools UserVoice channel.