Sometimes certain web pages in Firefox (FF) and html messages in Thunderbird (TB) the text can appear thin, ragged, badly rendered and hard to read. Even if you install the fonts the content uses onto your system it still appears the same. It seems that it’s necessary to disable bitmap font display for these fonts to avoid the ugliness in some web pages and emails. This HowTo is for content using the Calibri font in FF and TB and can be replaced with any compatible font.
This may also help font rendering in other applications like LibreOffice Writer under some circumstances.
Create or edit
Note: Add the sub directory
conf.dand create the file
Add these rows to the file
<match target="font"> <test qual="any" name="family"> <string>Calibri</string> </test> <edit name="embeddedbitmap"> <bool>false</bool> </edit> </match>
Restart your session and enjoy better looking content.
You can also disable embedded bitmap for all fonts, see link to Arch Wiki below.
Sources and more information: