You're right that mobile devices are harder to fingerprint – too many people with the same screen size, operating system, browser version, timezone, and languag

You're right that mobile devices are harder to fingerprint – too many people with the same screen size, operating system, browser version, timezone, and language/region settings. However, mobile devices have a bunch of sensors, some of which can be accessed by JavaScript without permission, namely the ones you wouldn't expect to yield identifying information (e.g. accelerometer). The problem is that no two sensors are alike – they all introduce noise into the data which can be enough to fingerprint a device. See here for a paper on the subject: https://crypto.stanford.edu/gyrophone/sensor_id.pdf https://crypto.stanford.edu/gyrophone/sensor_id.pdf