The Firefox web browser supports two types of themes: lightweight themes which were formerly known as Personas and are now commonly referred to as background themes or simply themes, and as a second type complete themes.
The difference between the two is that lightweight themes are limited in to what they can change in the browser. This means that you usually get a new background image for the browser but that is about it while complete themes may change icons and other user interface elements as well.
Mozilla plans to launch five lightweight themes with Firefox 34 as part of the organizations move to integrate themes into the browser's customization mode.
Note: Only the most recent version of the Nightly channel has access to the feature at the time of writing. It will take some weeks before Firefox Aurora, Beta and Stable users will be able to access the feature in their versions.
The browser's new customization mode was launched alongside Firefox 29, the version of Firefox that launched with the new Australis interface design.
When you open the feature with a click on the Hamburger menu at the top and the selection of customize from the context menu, you find the new Themes option listed there.
A click on it displays five recommended themes that Mozilla plans to renew in regular intervals. All themes can be previewed by hovering the mouse over them.
Doing so will apply the theme temporarily to Firefox so that you can see it in action in the browser. As soon as you move the cursor away, the current theme is displayed again.
To change to a theme simply click on it to do so. The default theme is always listed here so that you can change back to it easily using the customize menu or the appearance menu under about:addons which is opened when you click on the manage button.
The five themes that Mozilla has selected are the following ones:
- Carbon-light https://addons.mozilla.org/en-US/firefox/addon/carbon-light/
- Pastel gradient https://addons.mozilla.org/en-US/firefox/addon/pastel-gradient/
- Linen light https://addons.mozilla.org/en-US/firefox/addon/linen-light/
- Space Fantasy https://addons.mozilla.org/en-US/firefox/addon/space-fantasy/
- A web browser renaissance https://addons.mozilla.org/en-US/firefox/addon/a-web-browser-renaissance/?src=ss
Integration of theme switching options in Firefox's customization mode makes sense as it is related to that. While I'm personally not a fan of lightweight themes at all, it will certainly have its appeal to users who never came into contact with Firefox themes before or like lightweight themes and therefore the recommendations.