Font Fingerprint Test
Which typefaces are installed on this machine - measured without asking, and listed in full.
What this page read
🖐️ One vector is not a fingerprint
Nothing on this page identifies you on its own - it describes a class of machine. What makes a browser recognisable is several stable signals at once, which is what the full test measures and scores.
🖐️ Run the full fingerprint testFont Fingerprint Test
Websites cannot enumerate your fonts directly, so they measure instead: render a string in a candidate font with a known fallback, and compare the width against the fallback alone. A difference means the font resolved, which means it is installed. This page runs that comparison across a set of common typefaces and lists every one that answered.
Why installed fonts identify you
Fonts arrive with the operating system, with software installs, and with regional language packs. A machine with a design suite installed looks nothing like a fresh laptop, and a system configured for one language carries fonts another does not. The set as a whole is often more distinguishing than any single entry, and it is stable over long periods, because people install software rarely and uninstall fonts almost never.
What the count does and does not mean
A higher count generally means a more distinctive machine, but the relationship is not linear: a common set of twenty is less identifying than an unusual set of eight. The full list matters more than the number, which is why every detected font is printed here rather than a sample. Note also that this tests a fixed candidate list; a machine may carry hundreds of fonts this page never asks about, so treat the count as a sample rather than an inventory.
What reduces it
The Tor Browser bundles a fixed font set and refuses to use system fonts, so every user reports the same list. Firefox's resist-fingerprinting mode limits which fonts pages may use. Outside those, there is little to do: uninstalling fonts is impractical and would make you more unusual rather than less. This is one of the vectors where the realistic answer is a browser designed around the problem rather than a setting.
Font Fingerprint Test - FAQ
Common questions about this specific signal.
How can a website tell which fonts I have installed?
By measuring text rather than reading a list. The page renders a string in a candidate font with a known fallback and compares the rendered width to the fallback on its own. If the widths differ, the candidate font resolved and is therefore installed. Repeating that across a list of candidates produces a picture of your font set without any permission prompt.
Do installed fonts really make me identifiable?
In combination with other signals, yes. Fonts arrive with your operating system, your applications and your language settings, so the set reflects how a machine has been used and configured. It is also unusually stable - most people go years without changing it - which makes it valuable to trackers looking to recognise a visitor across long gaps.
Does this test see every font on my computer?
No. It tests a fixed list of common typefaces and reports which of those resolved. Your machine may carry many more that this page never asks about, so the count is a sample rather than an inventory. A tracker running a longer candidate list would learn more, at the cost of taking longer to do it.
Can I hide my installed fonts?
Not through an ordinary browser setting. The Tor Browser ships a fixed font set and refuses system fonts, so every user reports the same thing, and Firefox's resist-fingerprinting mode restricts font access. Removing fonts yourself does not help: an unusually small set is itself distinguishing, so the goal is to look like everyone else rather than to have less.
🧰 Related tests
Every test runs entirely in your browser - nothing is stored unless you choose to share the result.