Fixes for Firefox Proton

This is one of those things I’m publishing mostly so I can find it again. If it’s useful to you, cool.

If you haven’t tried Firefox since 2007, it’s worth revisiting. First because it’s independent and serves as a check against any single giant company controlling the web, but also because they’ve done really good work on the rendering engine and privacy in recent years.

That said, their new redesign that’s rolling out is not great. It’s picked up on two UI trends that make no sense to me.1

  1. Making the UI elements extra large, as if to prevent them from being a choking hazard to small children. This does not make sense on a 13 inch laptop where vertical space for content is scarce.
  2. Color schemes that consist of subtle shades of white in light mode and dark gray in dark mode. I don’t have a vision issue and this zero contrast pattern is hard to scan.

Fortunately, Firefox is also hackable. You can fix the UI size with three settings in about:config.

First, obviously set browser.compactmode.show to true, which brings the padding back down some the old version’s defaults.

I’ve set layout.css.devPixelsPerPx to 1.95, which brings it down from the Retina default of 2.0. This shrinks everything in the browser, chrome and content alike.

To compensate for the change in content, update toolkit.zoomManager.zoomValues, which is a comma delimited list, to include 1.05. Restart the browser, open the regular app settings, and set Default Zoom to 1.05.

Now the UI the content is normal size and the UI is subtle, no CSS hacks required.


Reinstating contrast in a way that doesn’t look broken with the split tabs is harder. The Arc themes (light, dark, split) aren’t terrible.

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