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Comment by crag | Hacker News Reader

Why fonts? Or do they use fonts as an ID?

Fonts are part of the fingerprint, especially if you know the OS. You take the set of installed fonts and subtract the set of OS default fonts, and you are likely to arrive at a unique key.

Take my corporate domain for instance: you could identify any machine on my domain since we'd all have a custom typeface installed (used on our company letterhead.) You could further identify our marketing coordinator, because she has a lot of strange typefaces used for signage and promotions. You could probably further identify me as a web developer since I have a lot of WOFF2 packaged fonts installed.

Side question -- do/could type foundries find pirate companies by looking at IP addresses using paid fonts without a license? Hardest part would be linking paid licenses to IP addresses, making individual unpaid usage harder to nail down. But if a company with dozens or hundreds of users at a single IP address all had a particular font installed, that IP was linkable to the company, and company didn't have a license, wouldn't that be pretty damning evidence?

Typeface piracy is otherwise pretty difficult to detect isn't it? Is it part of normal enterprise asset tracking / inventory systems?

Because every browser except the latest from Apple will happily tell every website you visit exactly what fonts you have installed. And that list changes very slowly over time, if ever, you know kind of like those patterns of skin ridges on your fingers.

It's one factor in a set of variables, that when combined can pinpoint you uniquely. This helps them overcome anti-tracking mechanisms like disabling cookies and such. Basically, by implementing this kind of technology, they know you don't want to be tracked and are attempting to do so anyway.

See the mechanisms used for this browser test, particularly the link for 'fingerprinting' after running the test: https://panopticlick.eff.org

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