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Making moves
Status: Trending idea
TLDR: popularize Firefox uC styles among regular users by representing them as content downloadable from AMO (just like regular themes) and promoting this 'advanced customization' as a unique feature and not something shady used only by "power users".

One of the greatest advantages of Firefox over other browsers is its interface is highly and easily customizable, thanks to using XUL for its UI. With minimal knowledge of CSS and 1-2 hours of learning you can change almost anything you want!

Firefox GNOME ThemeFirefox GNOME ThemeOne of a few dozens one-liner stylesOne of a few dozens one-liner stylesFlyingFoxFlyingFoxMaterialFoxMaterialFox

Knowing that, it's weird to see Mozilla doesn't do anything about this feature at all!
For example, to install the style, you have to enable uC support (labeled as "legacy stylesheets") in advanced settings which regular users won't ever go to, then find a style on potentially unsafe community forums, and then manually "install" it by moving it to the chrome folder.
Not to mention this feature seems to never was actively developed, not allowing to anyhow store several styles, having several security vulnerabilities etc.


So, what do I think Mozilla should do:

  1. Actively promote this feature as one of Firefox's benefits
    (because it is). Most Chromium-based browsers can only provide a very limited customization options, so Firefox will definitely stand out with this. Most of them don't even allow you to rearrange toolbar icons!
    For example, take a look at Vivaldi - one of its selling features is high (comparing to other Chromium-powered browsers) customization, and Firefox can potentially provide way more options!
  2. Improve the way userChrome works now
    The idea is to treat uC style the same as regular extensions and themes, providing config keys as extension permissions.
    This also means it'll require to ensure the uC style security (make a verification to protect browser from malicious sideload, fix possible security vulnerabilities (e.g. allow uC styles to load only other CSS files and PNG/SVG images) etc.) and maybe document some unclear parts of it somewhere on MDN.
  3. Create a section for userChrome styles on
    AMO Styles page mockup with a few themes showcased.AMO Styles page mockup with a few themes showcased.Since the sideload will no longer be an easy option (though still possible for debugging), people obviously would need a place where they can easily download uC styles they want.
    Why not provide them with one then?
    They also should be clearly distinguished from themes, as the first ones intended for simpler customization and most of uC styles are fully theme-compatible.


What do you think? Hope this suggestion will get some good feedback 🙂

Making moves

This would be a great move from Mozilla's point of view.  A real differentiator for Firefox (like you say), and if I was Mozilla, I'd love to put an end to the battles over UI changes, by giving non-expert users more freedom to choose their own look.

For example, most of the things that people (including me!) hated about Proton can be reversed in userChrome: if you could just download Lepton or similar from AMO, a lot of the complaints (which I'm sure were very draining for Mozilla folks) could have been avoided.

Not applicable

I would like the default theme to be simple and easily customizable with CSS. I also want it to be editable on a page like about:userchrome.

Not applicable

There are many userChrome on Github, but none of them had what I wanted, so I made my own. However, it is cumbersome to override the default CSS, and customizing the menu has not gone well yet.

Hackgets/Pale-Blue-Fox: Simple, flat and pale blue.

スクリーンショット 2022-06-20 141620.png

Making moves

I agree

Status changed to: Trending idea
Community Manager
Community Manager

Hey all,

Here with an exciting update…

Your idea has been upgraded to a “Trending idea.” This means it’s now one step closer to reaching our internal teams for review—learn more about The Idea Journey.

Please keep the conversation going (the more details, the better) and stay tuned for updates 😃

-The Community Team

Not applicable

@Jon Yay! I believe that the ability to customize the UI with CSS is a great advantage of Firefox. Shouldn't Mozilla be more open to UI design as well?

Familiar face
Making moves

This is my top wish by far, great write up.

Probably a reach but to take it further: Mozilla already being a massive learning resource for web-dev related topics, I'd like to see userChrome made accessible enough to a point where people unfamiliar with CSS or user interfaces entirely are compelled to pick up those skills through making their own style. Add documentation. Provide a short starter guide. Mozilla can tout Firefox as the tremendous 'learning by doing' sort of application it already is.

I remember using Firefox at school in 4th grade and just ogling at the 3d View feature and learning a lot about how sites are structured-- kids today would make their own userContent to put a memes on their about:home page, maybe picking up a taste for CSS/UI and learning more!

Firefox userChrome feels like such a unique tool in being able to practice and produce functional, usable, in depth UI design without having to build a program or settle for a website.


Strollin' around

Like 👍 

Strollin' around

This would be great! Yes, please.

New member

This is an excellent idea for the reasons in the original post. We need, however, to ensure that submitted userChrome-type code is not rejected on asthetic grounds and it should be remembered that the best judge of a "good" user experience is the user.

Making moves

a big +1 for this