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With certain Windows fonts there is a display issue where ligature-kerning seems to flip out and make the two letters bold. Here's a screenshot of an email using Helvetica in Firefox:

enter image description here

As you can see, it seems to be something about the way crossed characters (t and f) connect to each other and letters like i.

I've had this problem for a very long time (over multiple systems) and wondered if anybody has ever seen similar issues popping up and found a way to fix them.

Note: I think this does just affect Firefox. Chrome and LibreOffice are both fine.

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3 Answers 3

up vote 4 down vote accepted

lgarzo's answer will work only on websites that have a "noligs" class on the text (most websites don't).

To globally disable ligatures on all websites, add the following line to your userChrome.css:

* { -moz-font-feature-settings: "liga=0"; }

The easiest way to do that is to create a new style with the Stylish extension.

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+1 for the Stylish suggestion. AFAIR I've quoted Mozilla documentation (since I had expected the OP to be able to transform that as he wished :)) My intention was to include the rule into the page's CSS. (Cannot check the source, though. It seems to be down ATM.) – lgarzo Jul 5 '12 at 18:50

Another solution that will work with all applications, including Libre Office, is given by aldeby:

Edit or create the file ~/.fonts.conf and paste this code in it:

<match target="font" >
<edit name="embeddedbitmap" mode="assign">

Make sure to keep the XML structure.

Log out and in again, and Calibri (and possibly some other fonts) will look much better (actually even better than with the other answers given here, because the ugly bitmap substitutions are completely disabled).

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This one's a better solution than the earlier ones, as it's a global fix, and eliminating ligatures is a bodge. Ligatures are there to make text more pleasing to read, and to turn them off to work around a configuration problem is not ideal. – scruss May 20 '13 at 13:58

A few remarks popped into my mind while looking at the image:

  • The ligatures seem to be anti-aliased, while the rest of the text is not. Therefore it looks fatter than normal text (although I cannot deny it also looks bold).
  • AFAIK the Helvetica font is a non-standard font, i.e. does not come with default Windows installations. Do you have it installed, or is it a different font?

I think the problem is based on the font not supporting ligatures/kerning correctly.

You can disable ligatures in FF with the CSS rule below:

/* disable common ligatures, usually on by default */
.noligs { -moz-font-feature-settings: "liga=0"; }

Source: CSS Reference:Mozilla Extensions

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