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Over the last few days I've noticed that the fonts rendered by Firefox are bolder than usual. This affects me both as a user, as the fonts are jarring and noticeably harder to read, and as a web developer who does most of his development in Firefox, as it points to an increase in stylistic inconsistency between Firefox and Chrome, meaning that my users are essentially experiencing two different versions of all the sites I design.

Checking Firefox's update history in Help > About tells me that it was updated to Firefox 109 on January 17, which roughly coincides with the time I noticed this issue. However, checking the update's (very minimal) changelog doesn't mention anything about changes to fonts or typefaces.

Is there any confirmation of if and when exactly this change was implemented in Firefox, or is something else responsible for it? If it is a result of the update, what was the reasoning for it?

Hashim Aziz
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1 Answers1

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Update: this change has now been reverted

Following on from the discussion in the original bug report, this change was reverted in the following commit, meaning future versions of Firefox will render fonts just like version 108 and previous did. Thanks to all those involved, including those who voiced their opposition to the change on the bug report, and credit where it's due to Mozilla and the Firefox devs for responding to and resolving the issue in less than a week.

To get an update that contains the fix, you can temporarily switch to the Beta update channel by installing the latest Beta build of Firefox here, where the fix has already been pushed. Beta is the most stable update channel after the standard Release channel. A Release channel update with the fix will probably be issued in about a month.

If you previously applied the workaround below, remember to undo it by going through the same steps, but changing gfx.font_rendering.cleartype_params.gamma back to -1 instead of 2200. Doing this before you update will make sure you actually notice the difference, and can confirm that the update worked for you.

Although not listed in the changelog, this was indeed a change introduced in Firefox 109.0, and is due to the "fixing" of a bug which previously caused Windows Cleartype settings to be ignored. The problem is that Firefox seems to be the only browser that has bothered to fix this bug, making it look more inconsistent with Chrome than it ever and resulting in text that is jarring to read.

As a short-term solution, you can try running Windows 10's Clear Type Tuner (which for me only resulted in a larger discrepancy between the boldness of header and body text) or following the instructions below. For a more permanent fix, see the final section.

Workaround: reverting the change for your system

  1. In Windows' Registry Editor, navigate to the Computer\HKEY_LOCAL_MACHINE\Software\Microsoft\Avalon.Graphics\DISPLAY1 key

  2. Look for the GammaNote value, and take note of its data in brackets (it will likely be 2200)

  3. Navigate to about:config from the Firefox address bar, and search for "gamma".

  4. Modify the value of the gfx.font_rendering.cleartype_params.gamma config key to the value previously noted, and click the ✓ to apply the change.

  5. Finally, navigate to about:profiles and click Restart normally to restart Firefox

Thanks to Fanolian for providing the basis for these instructions and finding the relevant Registry keys.

Permanent fix: reverting the change for future versions of Firefox

The above instructions are a short-term fix for individual power users who are bothered enough by the change to revert it - for the vast majority of Firefox users, this change will be the new default, which means unless it's reverted by Mozilla itself, the new uglier fonts will be the new Firefox experience for every version going forward.

Therefore, if you're a web developer or just someone who values a consistent browser experience across Windows, I recommend voicing your views on the change via the relevant Bugzilla issue. With enough users opposed to it (which seems to be quite a lot, if Reddit is anything to go by) there's a chance the devs will see sense and revert the behaviour to look readable and consistent with other browsers once again.

Hashim Aziz
  • 13,835