My OS is Windows 10 Pro 64-bit. Font blocker 1.21 doesn't work with Firefox 153.0.1 (64-bit) + Firefox ESR 153.0.0 (64-bit). Old comment published 7 years ago "Thanks Rudie, it works fine with Firefox 68.0.2" .

literally so useful, i can finally block the new york font from showing up on wordpress webpages. i love whoever created this extension!!! THANK YOUUUU

Issues: 1) replaces to Arial!!! My eyes are bleeding. Should better have a user-configured default sans font; 2) replaces monospaced to Arial!!! My eyes are bleeding. Should better have a user-configured default monospace font; 3) replaces serif to Arial!!! My eyes are bleeding. Should better have a user-configured default serif font. 4) Probably breaks font metrics, so on-line editors misplace text caret. For me it's definitely broken. Otherwise extension is working good, it really makes all those mad designers to behaviour nice. But with 1-4 problems, this extension is useless.

Works perfectly as intended, really saved me after having some issues with antialiasing on specific Microsoft fonts.