Debian – Firefox Quantum on Debian stretch font rendering problems

I've had this issue for ages, maybe it's time to do something about it!

It comes done to ClearType, Microsoft and patents from what I read. Most *nix distro's disable any patent protected font rendering by default.

Read about Debian and fonts here, you want Subpixel-hinting and Font-smoothing section.

There's a config file on that page but I will add here for future reference. Create a file called .fonts.conf in your home directory, and add the following:

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
 <match target="font">
  <edit mode="assign" name="rgba">
   <const>rgb</const>
  </edit>
 </match>
 <match target="font">
  <edit mode="assign" name="hinting">
   <bool>true</bool>
  </edit>
 </match>
 <match target="font">
  <edit mode="assign" name="hintstyle">
   <const>hintslight</const>
  </edit>
 </match>
 <match target="font">
  <edit mode="assign" name="antialias">
   <bool>true</bool>
  </edit>
 </match>
  <match target="font">
  <edit mode="assign" name="lcdfilter">
    <const>lcddefault</const>
  </edit>
  </match>
</fontconfig>

Go to about:config Find the preference gfx.font_rendering.cleartype_params.rendering_mode Change its value (probably -1) to 1

1 turns anti-aliasing off. You might also want to try 2 and 3.

4 and 5 are not your friends, they involve anti-aliasing.

That turns off both anti-aliasing, and font-hinting.

OR You Can Try Belows

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
  <match target="font">
    <edit mode="assign" name="lcdfilter">
      <const>lcddefault</const>
</edit>
  </match>
  <match target="pattern">
    <test qual="any" name="family"><string>Liberation Serif</string></test>
   <edit name="autohint" mode="assign">
   <bool>false</bool>
   </edit>
  </match>
</fontconfig>