Subject: Firefox 153 scrollbar behavior change feedback

[se23xx]

Hello Firefox team,

I would like to share my feedback about the scrollbar behavior change introduced in Firefox 153.

After this update, some websites that use webkit scrollbar CSS rules behave differently in Firefox. Previously, these websites displayed overlay scrollbars, but now some of them show a separate scrollbar area with an additional line next to the scrollbar.

I understand that the goal of this change is to improve compatibility with websites designed for Chromium-based browsers. However, this also changes the visual experience for Firefox users.

Many users may prefer the previous overlay scrollbar behavior. The new behavior can make some websites look less clean and inconsistent compared to previous Firefox versions.

Could you consider adding a preference that allows users to disable this compatibility behavior and keep the previous scrollbar behavior?

I appreciate the work done to improve web compatibility, but giving users more control over this change would be a better solution.

Thank you for your work on Firefox.

Best regards

[wrtr]

Agree. This is a very bad bandage patch. As a web app developer, this css scrollbar change causes issues in visual use in firefox web app visuals that people had just gotten used to, while not actually supporting the Chromium-based browsers or ::-webkit-scrollbar css options. It does neither. Either support the standard CSS, or support both it and the ::-webkit-scrollbar css options. But to just turn off overlay without giving any of the options for developers to fix things after it's turned off, based on css meant for other browsers and not firefox is just... well... bad.

We like firefox, we like you, we'd like people to use it. This change causes cracks in firefox usage. Choose one road or the other. But choose. Much thanks. This seems like a bad unneeded AI created change, put in to support....other browser's code? Scratches head. If you don't support ::-webkit-scrollbar css options then just not support it and support/force standard css. Or support ::-webkit-scrollbar css options. A bandage that breaks your code to not really support other browser's code is bad... Why turn off overlay when seeing another browser's css code? As Marge Simpson would say...hrrrrrrmmmmm...

[aslexnalver234]

Thank you for the detailed feedback. The behavior change you're seeing in Firefox 153 comes from newly added, limited support for the non-standard ::-webkit-scrollbar pseudo-element, which was introduced specifically for web compatibility. Many popular sites (Gmail, Google Calendar, Twitch, Discord, and others), including tools such as Conversor de Letras, ship CSS written only for Chromium's -webkit-scrollbar rules. Previously, Firefox ignored these rules entirely, which sometimes caused nested scrollbars to stack on top of each other or become unreachable when a site hid its "fake" scrollbar with display: none or width: 0.

In Firefox 153, if a site defines a ::-webkit-scrollbar rule with a non-zero width or height, Firefox now disables the overlay scrollbar for that specific container and shows a classic, separate scrollbar area instead, which is the "additional line" you're noticing. Full WebKit-style scrollbar customization (colors, border-radius, etc.) is still not supported—only this narrow compatibility behavior was added.

At the moment there isn't a dedicated toggle in Settings for this specific compatibility behavior, but you do have a couple of workarounds while you wait on a possible future preference. You can override scrollbar appearance globally through about:config by adjusting widget.non-native-theme.scrollbar.style and related widget.non-native-theme.scrollbar.* keys, or use a userContent.css stylesheet to force scrollbar-width and scrollbar-color on specific sites, since the standard scrollbar properties take precedence over ::-webkit-scrollbar rules when both are present.

Your suggestion of a dedicated preference to fully opt out of this compatibility shim is a reasonable one worth filing as a formal feature request on Bugzilla (under Core > CSS Parsing and Computation or Core > Layout) so it can be tracked and considered by the engineers who own this change, since Connect threads like this one are read as feedback but aren't a substitute for a tracked bug report.

[wrtr]

OK.... AI response bot... tech ...splaining a dev and automatically assuming that I didn't read the spec, or that the other person didn't read the spec, and auto-repeating things, when they were outlined in the feedback form responses to this ... is just off-putting and well bad...and bad form. And that's me using kind words. And a good way to lose your user/development base.

If you are going to offer breaking bandage support, to support other browser's code then implement the support for ::-webkit-scrollbar in Firefox entirely instead of a bandage firefox breaking change that affects everyone in the world for every web page using your Firefox browser, all your firefox users, and any developer's websites, pages, and apps running or displaying on firefox.

As any web developer, displaying their web pages or web software in a firefox browser, we can't ask everyone in the world to turn off the bandage breaking changes in their browser, especially in a tech hidden software screen.

You are the only web browser that doesn't support ::-webkit-scrollbar. Support it, and you too can have nice scrollbars. And keep your user base.

You want to support popular sites like (Gmail, Google Calendar, Twitch, Discord, and others), including tools such as Conversor de Letras. Then support the ::-webkit-scrollbar spec, the code they base their scrollbars on. Instead of breaking firefox browser things, and the firefox user experience, just to support other browser's code. Support the ::-webkit-scrollbar spec in firefox, to support those sites.

When regular web users see odd changes happen in your browsers working that happen(for them out of the blue), and see enough of them happen, they aren't going to spend time looking for things to fix and more work. They are just going to quit using firefox and and move to using software on a different browser they can trust.

Standard scrollbar properties do not take precedence currently in Firefox since the change, as overlay scrollbars are automatically turned off whenever firefox sees ::-webkit-scrollbar rules. Breaking the visuals and displays in hundreds of thousands of firefox displayed websites and website pages. Making seeing things in firefox look odd to them.

You feel you are forced to support the ::-webkit-scrollbar to keep your market share, fine. Then support the ::-webkit-scrollbar in firefox and be done with it. At some point a spec like it will happen anyhow.

Again, we like you, want to see you stick around. Make the support change, don't penalize the visual displays in Firefox and your user base.

Best,