Since I upgraded my Firefox from 90.x to 91.0, all websites I visit seem to suffer from messed up styling.

Three example screenshots, but it's not restricted to any particular site, it happens everywhere:

screenshot (→ full resolution)

screenshot (→ full resolution)

screenshot (→ full resolution)

As you can see, it's as if there is a white background being enforced behind all text. As if part of the CSS is being ignored or overruled or something.

I've already tried all the obvious steps:

  • closed and restarted browser
  • cleared cache and local data
  • disabled all extensions, plug-ins and add-ons
  • refresh everything
  • rebooted laptop
  • checked view/display options, didn't notice anything weird (and haven't touched these anyway)
  • not using any VPN or proxy or whatever that could theoretically tamper with any content

This only happens in Firefox since I upgraded to 91.0. Didn't happen before, and doesn't happen in other browsers i.e. Chrome, Safari, etc.

Sometimes it's just disturbing, sometimes it makes sites completely unusable.

FYI I'm using macOS 10.15.6 Catalina.

Any idea what can be causing this and how to get rid of it?

  • Check if in Settings > General > Colors... you need to uncheck "Use system colors" and if you have changed the drop-down box to anything else than the default "Only with High Contrast themes" (are you using a High Contrast theme?).
    – harrymc
    Aug 13, 2021 at 13:37
  • @harrymc Thanks but no I'm not using a High Contrast theme. Also the 'use system colors' was already unchecked, and the drop-down box is "Only with High Contrast themes".
    – Rog
    Aug 14, 2021 at 6:42

1 Answer 1


I was having the exact same issue, it happened completely out of the blue when v91 landed. As per a comment on your question by @harrymc I went to Settings (Cmd+,) > General > Language and Appearance > Colours… and then changed the "Override the colours specified by the page with your selections above" dropdown to "Never". Everything started working correctly again. This isn't an option I've ever changed, and I have no idea why it should suddenly break every single website starting from FF v91, but there you go.

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