1988629 - [meta] Disable theme colors in forced colors mode (windows high contrast mode)

Status: NEW

(Toolkit :: Themes, task)

Description

[Jared Hirsch [:jhirsch] (he/him) (Needinfo please)]

In forced colors mode, Firefox inconsistently mixes colors from the current Firefox theme and the forced colors palette supplied by Windows. This inconsistent application of colors leads to a wide variety of bugs. Note that these bugs only affect Windows users: Mac and Linux accessibility settings offer increased contrast, but not forced colors.

The profiles team encountered many contrast bugs caused by the mix of profiles theme colors and forced colors in the browser UI. After discussion[1] with experts from the add-ons, accessibility, and DOM teams, we plan to resolve this class of bugs for Firefox as follows:

• disable theme colors in forced-colors mode
• add a "themes disabled" warning message to the about:addons page, and show it when in forced-colors mode
• put both changes behind a pref so we can revert the behavior if something breaks in release

We considered whether we might break Firefox for forced-colors users who use Firefox themes, but telemetry data[2] shows that most forced-colors users have the default theme. So, we expect that these changes will improve Firefox accessibility for most forced-colors users.

[1] https://docs.google.com/document/d/1vonoQnVsJWbbU0QbUAuctyRPr7RxI6uxjieiH5WS14o/edit?tab=t.0 (note 9/15/25: working on making this document world-readable)
[2] (https://sql.telemetry.mozilla.org/queries/110393#271010)

Comment 2

[MarjaE]

But users stuck with Windows may need high-contrast themes to use the Settings, the @#$% File Explorer, etc. and need other themes in Thunderbird, e.g. because the high-contrast theme hides the outlines of the scrollbars.

Comment 3

[3be]

(In reply to Jared Hirsch [:jhirsch] (he/him) (Needinfo please) from comment #0)

We considered whether we might break Firefox for forced-colors users who use Firefox themes...

In reply to your comment in another bug that is closed (https://bugzilla.mozilla.org/show_bug.cgi?id=2005600#c6):

If you'd like to customize the colors in Firefox, you can either customize your OS contrast theme...

The problem is that we cannot customize the color that Firefox is using for many parts covered by Firefox themes, like the tab bar, menu bar, side bar with vertical tabs. Please see my report in bug #2014672.

I would like to be able to use Firefox themes even with Windows Contrast themes, because I could choose a Firefox theme that is better to my vision than the non-configurable ActiveCaption color that is currently used. I think changing pref in about:config, which you could remove in the future, is not the best solution.