By rendering text in 60 different fonts and measuring pixel widths, this page detects
which fonts are installed on your system — without any permission, in under one second.
Your font set is a fingerprint of your OS, region, and software stack.
60 font measurements. No permission asked.
Your installed fonts identify your operating system, region, corporate software stack,
and language. This technique has been used for cross-site tracking since 2010 and remains
effective even in private browsing mode.
—detected
—not found
—inferred os
press scan to detect installed fonts
osscanning...
regionscanning...
softwarescanning...
▶ how font detection works
The technique is simple: create a hidden canvas, render the same string in two fonts simultaneously — the font being tested, with a monospace fallback. Measure the resulting text width.
If the tested font is not installed, the browser falls back to the generic monospace font and the width matches the baseline. If the tested font is installed, it uses that font's metrics — different character widths, different result.
The test string mmmmmmmmmmlli is chosen deliberately: it maximises the width difference between proportional and monospace fonts, making detection more reliable.
Font sets reveal a great deal:
Calibri, Segoe UI, Cambria — Microsoft Office / Windows installed
SF Pro, San Francisco, Osaka — macOS or iOS device
Ubuntu, Cantarell, Fira Sans — Linux desktop (GNOME/KDE)
Noto CJK, SimSun, SimHei — Chinese locale or language pack
Malgun Gothic, Gulim, Batang — Korean locale
Hiragino, Yu Gothic, Meiryo — Japanese locale
Arabic Typesetting — Arabic locale or Windows Arabic pack
This technique requires no permission and works in all major browsers. Brave Browser adds noise to canvas measurements which may reduce accuracy slightly.