I was trying to reproduce fluttercommunity/font_awesome_flutter#54 when I found that the icons were loading fine in chrome, but not in firefox. I did some digging and found some inconsistencies in the flutter font loading behaviour. Chrome loads the icon fonts, but does not even try to load Roboto - and firefox tries to load Roboto, fails with a 404, and ignores the custom icon fonts. For some reason both are able to load the material icons font file (and display material icons).

The content of FontMainfest.json both browsers received was the same and there were no browser addons blocking anything.

How to reproduce: Create a new flutter project, add font_awesome_flutter as dependency and use an icon (e.g. Icon(FontAwesomeIcons.book)) anywhere.