To enhance privacy and protect myself against fonts fingerprinting in Firefox, I have set in about:config: browser.display.use_documents_fonts = 0. This setting is meant to disable websites' ability to detect installed fonts.

With JavaScript enabled, I can test which fonts are visible at Browserleaks. When this setting is 1, nearly 200 fonts are detected in the category CSS+JS Quick Test. In the past, setting to 0 would show 0 Font detected. Now I have a new computer; even when browser.display.use_documents_fonts = 0, there are still 5 fonts detected. These are the MingLiU fonts.

Browserleaks detects MingLiU fonts even with protection turned ON

I can find these fonts in C:\Windows\Fonts along with many other fonts. I have tried restarting Firefox with a completely fresh profile (no extensions or plugins, or other customization) and I observe the same behavior. I am running Firefox 41 on Windows 7 x64

My question is simple: why are these fonts still showing up when browser.display.use_documents_fonts = 0? How can I prevent that from happening? I hope to find something short of deleting the fonts because I don't know whether an application needs them.

  • I didn't get any help here. After a while I decided to delete the fonts. Windows refused with an error message to the effect that they are protected system fonts and cannot be deleted. I followed the first 4 steps from this wikihow.com article and successfully deleted them. – BeetleJuice Oct 13 '15 at 12:06

I see that I am late with my answer as you already uninstalled those fonts from your system. If you decide to reinstall those fonts you can prevent their enumeration by doing the following:

Go to about:config. Search for font.blacklist.underline_offset Select it and right click to modify. Delete MingLiU,MingLiU-ExtB,MingLiU_HKSCS,MingLiU-HKSCS-ExtB and PMingLiU,PMingLiU-ExtB Make sure to remove extra comas as well. Click ok Restart Firefox. Go to browserleaks.com and check that they are not enumerated anymore.

  • I can't verify this anymore since I no longer have the fonts but I appreciate you taking the time to answer. – BeetleJuice Oct 26 '15 at 8:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.