Re: [csswg-drafts] [css-scrollbars-1] Add `scrollbar-style` property for `overlay` scrollbars (#13218)

That is an excellent point and a very important clarification. My apologies for mixing up browser defaults and system preferences, especially regarding Firefox on Windows.

You are correct: the risk is that the author's `scrollbar-style: overlay` would override what is essentially an accessibility preference for a fixed scrollbar, regardless of whether that preference comes from the OS or a browser setting.

### Proposed Hierarchy for Scrollbar Rendering

To ensure **User Accessibility Intent** always wins, we must define the behavior hierarchy as follows:

1.  **Highest Priority: User Preference Override**
    * If the user has enabled a setting (either in the OS like "Always show scrollbars" on Windows, or in the browser like Firefox's "Always show scrollbars" setting) that indicates a desire for a **fixed/non-overlay scrollbar**, the author's `scrollbar-style: overlay` must be **ignored**, and a fixed scrollbar must be rendered.
2.  **Second Priority: Author Request**
    * If there is **no explicit user preference** for a fixed scrollbar, then `scrollbar-style: overlay` is respected, and an overlay scrollbar is rendered.
3.  **Lowest Priority: Browser Default (Implicit Intent)**
    * If `scrollbar-style` is `auto` (or if it defaults to an implicit value), the browser renders its platform-specific default (overlay on macOS/Firefox, fixed on Chrome/Windows, etc.).

This hierarchy ensures that users who rely on the fixed visual presence of a scrollbar are never disadvantaged by an author's stylistic choice, while still giving authors the tool they need to solve the cross-platform layout issues on Chrome/Windows when a fixed scrollbar is *not* explicitly requested by the user.

Does defining this strong **User Preference Override** clarify the desired behavior and address your concerns about authorship overriding user accessibility settings?


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Received on Monday, 15 December 2025 13:50:32 UTC