Firefox 16 Coming October 9th – Memory And Technical Improvements

Firefox 16 is due to be released tomorrow (from Tuesday October 9th). It includes a variety of new features and improvements, especially in memory management and responsiveness – there are few user interface changes this time around. New features include:

  • Improved JavaScript responsiveness via incremental garbage collection (GC) – improved memory management. This is a major feature, over a year in the making, that makes Firefox smoother and less laggy – it should respond more quickly to mouse clicks and key presses. Animations and games will also draw more smoothly.

Firefox 17 and 18 will have additional improvements that will decrease pause times even more. Tech Note: Garbage Collection (GC) refers to the freeing up of memory which is important for performance. Put simply, the GC tries to reclaim garbage – memory occupied by objects that are no longer in use e.g. Firefox tabs which have been closed.

Performing GC in one big job can cause a slowdown – Firefox can’t do anything whilst the process is running. The idea of doing it incrementally is to only do a little bit of GC at any one time. Overall, the same amount of time is spent doing it, but each individual pause (whilst it is performed) is shorter. With shorter GC pause times, games and other dynamic content on the web should have shorter pauses – hopefully so short that users can no longer notice them.

  • Firefox on Mac OS X VoiceOver support – now has preliminary VoiceOver support turned on by default
  • Support for SPDY networking protocol v3 – support for the latest version of SPDY to improve speed and responsiveness of supported sites e.g. Google, Twitter, Facebook.
  • Initial web app support (Windows/Mac/Linux) – Web apps are apps built using standard Web technologies – Gmail and Twitter are Web apps. Small additions to existing sites can turn them into apps that run in a rich, fun, and powerful computing environment.
  • Changed context (right click) menu – removed the ‘Send Link…’ item and combined the ‘Stop’ and ‘Reload’ items as shown below. The Stop and Reload toolbar icons have also been removed (previously available via Customize Toolbar).

Tip: We have reviewed how to  add back ‘Send Link’ via email option into the right click menu.

FF context

  • Acholi localization added – Acholi is an ethnic group from Northern Uganda and South Sudan

In addition, there are many technical (under the hood) updates in Firefox 16 such as a new Developer Toolbar and a new command line for quick keyboard access – the video below explains it:

There have also been CSS enhancements and per tab reporting in about:memory.

End Of Support For OS X 10.5 Leopard – Firefox 16 is the final release to support Mac OS X 10.5 (Leopard) – users will stop receiving Firefox updates (including new features and security fixes) from November 20th. Leopard users will need to upgrade to Snow Leopard or Lion to use Firefox 17 onwards. Note that Google Chrome has also just ended support for Leopard.

New Features Present But Disabled By Default In Firefox 16 – These are new features introduced in the last couple of Firefox releases which haven’t yet been enabled – whilst they work ok for me it is possible they could have outstanding bugs.

The more adventurous user (or those wishing to get an early view of future Firefox features) may wish to enable them – they can easily be disabled again if they cause any issues.

1. The new Click to Play feature (configure plugins to only load on click) is still not enabled by default. However, you can activate it via a change in about:config – see Activating Click To Play.

2. The new In Content Preferences (Firefox Options open in a new tab instead of a separate window) is still not enabled by default. However, you can activate it via a change in about:config – see Enable In Content Preferences.

3. The new panel-based Download Interface (progress of downloads opens in a panel instead of a separate window) is still not enabled by default. However, you can activate it via a change in about:config – see Enable New Download Interface.


The memory improvements in Firefox 16 are welcome and technical changes help keep it compatible with the latest web standards.

As usual, this new version of Firefox will be available to users from October 9th over several days (to avoid overloading Mozilla’s servers) – if you check for updates (via Firefox Menu \ Help \ About Firefox \ Check For Updates) and find there are none available for you yet, just try again a day or two later.