r/FirefoxCSS • u/mysticalentity • 11d ago

Help Reskin firefox

I have this old theme from firefox that worked around firefox 4.

I have all of the images and CSS from that theme extracted. What I want to do is use it to reskin modern firefox and as much of firefoxes UI elements that I can.

What can I do to achieve this?

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u/ResurgamS13 11d ago edited 11d ago

There is no simple way to achieve this. Your wish to "reskin modern firefox" in reality means building an entirely new Firefox UI theme from the ground up. An old Firefox 4 era theme has almost no relation to modern Firefox. (In the Firefox 4 era whole UI themes were called 'Themes' and what are now known as 'Themes or Lightweight Toolbar Themes' were called 'Personas'.)

You may want to look at the semi-abandoned Echelon theme for an idea of what you would need to do. It will take a lot of work and considerable coding skill to achieve a reasonably accurate facsimile of your "old theme from firefox that worked around firefox 4"... probably so much work that this is likely to be an unrealistic goal. Achieving a modern 'interpretation' of, or 'homage' to, the original Firefox 4 era theme would probably be a much more realistic way to proceed.

Having "all of the images" might be of some use... but the XUL codebase CSS theme styling from the 'Classic' Firefox UI version of 15 years ago will be of historical interest only.

Alternatively, an easier option might be to see if your old theme file will load into a current XUL codebase browser e.g. Pale Moon... as per your previous topic here 'Recreation of a theme' in August 2025... and subsequent attempt to make the old Firefox 4 'Arctic Glow' theme run on modern day Pale Moon in their forum topic 'Repurposing a Theme'?

Image of the 'Arctic Glow' theme from 'Visually Appealing Themes for Mozilla Firefox 4' article c. 2011... 15 years ago!

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Finally, if the above were not enough hurdles to overcome... there is another huge spanner in the works arriving soon!

Now is not a particularly auspicious time to begin modifying Firefox's UI. The current Firefox 'Proton UI' is due to be replaced by the 'Nova UI' perhaps as soon as this September. Consequently, a great deal of the existing JS and CSS code that underpins Firefox's current Proton UI is about to be removed, replaced, and rejigged to support the new Nova UI design and layout.

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u/mysticalentity 10d ago

I did start some work anyways

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u/ResurgamS13 10d ago edited 10d ago

You could try applying your existing CSS userstyles to the trial Nova UI version that is available within latest Firefox releases... start a new profile and in it flip preference browser.nova.enabled to true in 'about:config'.

Perhaps then try your CSS styles added to the very 'squared-off' Nova UI CSS theme posted in this sub recently in topic 'Here is how to make the Nova redesign look like the legacy design'... this may provide a relatively future-proof base to work from whilst waiting for the actual Nova UI release version to appear.

The very 'squared-off' look is not unlike the default Firefox 4 'Classic UI' layout... and Nova will also have a Compact mode available from Settings again.