Firefox 15 has been released today (Tuesday 28th August). It includes a variety of new features and improvements – plus one that some users may not like…
New Features in Firefox 15
- ‘Tabs on Top’ option removed from new installs of Firefox – this will annoy some people who prefer to keep tabs on bottom… You used to be able to tick/untick the ‘Tabs on Top’ option from Firefox \ Options or by right clicking on the toolbar – it was easy to enable/disable it in this way.
Firefox 15 removes the ‘Tabs on Top’ option from both places – if you (re)install it from scratch. If you upgrade to Firefox 15 it will keep your existing settings and menu options intact. However, if you install Firefox 15 from scratch it will default to Tabs on Top – with no user interface way to change it.
Fortunately it is still possible to change it via about:config preferences as detailed below:
- Open Firefox and type about:config in the address bar and press Enter. Click the “I’ll be careful I Promise” warning button (if it appears) to reveal a long list of preferences used in Firefox.
- Double click the browser.tabs.onTop preference to change it from ‘true’ (the default) to ‘false’ – this moves tabs to the bottom again i.e. below the toolbars.
Tip: You can scroll down the list of preferences but the quickest way to find it is to type part of the preference name e.g. onTop into the Search box at the top of the config page
[Double clicking the preference again will change it back to 'true' and re-enable tabs on top].
- Start-up performance improvements – Leverages the Windows maintenance service to improve Firefox’s start-up time.
- Memory Improvements – Reduces memory leaks caused by some add-ons.
- Silent update: Background updates – Moves the bulk of the update process to the current session so that when the user restarts, there’s not much left to do to complete the update and it appears as if no interruption actually happened. This only applies to Mac/Linux – for Windows, the Mozilla Maintenance Service will do this.
- Accessibility Improvements – Accessibility support for Mac improved.
- In Content Preferences – The Firefox Preferences (Options) window has been moved into the content area i.e. appears in a new tab instead of a separate Options window.
The goal is to eliminate Firefox’s separate management windows in favor of in-content designs. This setting is disabled by default in Firefox 15 but you can enable it right now by following my guide here.
- ‘Don’t Load tabs until selected’ – This menu option has been moved from the ‘General’ tab to the ‘Tabs’ tab in the Options window as shown below – it does make more sense to have it there:
Technical (under the hood) Changes in Firefox 15
- DEVELOPER – Responsive Design View. Allows developers to quickly emulate different screen sizes to see how their designs react to the change.
- DEVELOPER – Detailed element layout view. The purpose of the Layout tool is to help the user see detailed information about the final dimensions of a page element.
- DEVELOPER – The CSS word-break property has been implemented.
- HTML5 – Native support for the Opus audio codec added.
- HTML5 – The <source> element now supports the media attribute.
- HTML5 – The <audio> and <video> elements now support the played attribute.
Changes Not Implemented in Firefox 15
Incremental garbage collection (GC) – the change to enable incremental GC by default was pulled from Firefox 15 due to some outstanding issues. The idea of incremental GC is that games and other dynamic content on the web will have more tolerable pauses, and in some cases will go from having pauses that users notice to not having pauses that users notice.
Although this feature is included in Firefox 14 and 15, it is still disabled by default and not officially supported due to known issues – it is likely to be implemented in Firefox 16. If you really can’t wait you can enable it right now (recommended for advanced users only) by following my guide here – disable it again if you have any problems.
Support for SPDY networking protocol v3 – support for the latest version of SPDY to improve speed and responsiveness. This has been moved to Firefox 16.
There are a lot of changes in Firefox 15 – in particular, start-up performance and memory improvements are welcome changes.
Technical behind the scenes features help keep Firefox up to date with the latest web standards.
The removal of the ‘Tabs on Top’ option from new installations may annoy some people – it seems to be of more benefit to Mozilla designers than Firefox users… Yes, it can be changed via about:config but it’s a pain to do if you need to reinstall Firefox or install it on a new computer – the old menu option was far simpler.
As usual, this new version of Firefox will be available to users from August 28th over several days (to avoid overloading Mozilla’s servers) – don’t worry 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.