The latest release 49 of Firefox comes with some interesting new features. Here’s what they mean for Fedora users and how to enable them beyond default setup.

Make a safe playground

When you’re testing Firefox, you should create a new fresh profile. If something goes wrong, you won’t lose data. The extra profile also allows you to run additional instances at the same time, each with a different configuration.

Open a terminal and create a new Firefox profile:

$ firefox --ProfileManager

Then run your profile:

$ firefox -P profile_name --no-remote

The –no-remote parameter launches an independent instance, instead of connecting to a running one.

Now for the fun part! Type about:config in the location bar to bring up hidden configuration options. The remaining tips in this article require you to edit these configuration keys. All changes usually require you to restart the browser.

Graphics acceleration

Firefox integrates the Skia graphics library as seen in Google Chrome. Unlike Cairo, the former default, Skia promises faster and parallel graphics rendering on Linux.

Skia is not yet enabled completely, but only for canvas HTML5 elements. For a full Skia experience, which may provide anything from ultra-speed to a crash on startup, set gfx.content.azure.backends to skia.

Electrolysis

Electrolysis not only dissolves water but is also meant to speed up Firefox. When Electrolysis is enabled, all web content runs in a separated process under the plugin-container, emancipated from the main browser.

Firefox 49 is a bit picky, and not every piece of content will work this way. To check content status, open the about:support page and look at the Multiprocess Windows row. If some content is not working with Electrolysis, you can try other options to tune the function. A good start is to disable incompatible extensions and set browser.tabs.remote.autostart to true.

For more instructions, including how to force-enable Electrolysis, refer to the Mozilla Wiki.

Dark times are back

At least for your browser, they are. If you like dark themes on the desktop and want the same for the web, toogle widget.allow-gtk-dark-theme to true. Firefox will use a default dark theme for both the user interface and web content.