I was curious after posting some hints about how to protect your privacy to see how they worked.
Using EFF’s convenient panopticlick browser fingerprinting site. Panopticlick doesn’t use all the tricks available, such as measuring the time delta between your machine and a reference time, but it does a pretty good job. Most of my machines test as “completely unique,” which I find complementary but isn’t really all that good for not being tracked.
Personally I’m not too wound up about targeted marketing style uses of information. If I’m going to see ads I’d rather they be closer to my interests than not. But there are bad actors using the same information for more nefarious purposes and I’d rather see mistargeted ads than give the wrong person useful information.
Testing Panopticlick with scripts blocked (note TACO doesn’t help with browser fingerprinting, just cookie control) I cut my fingerprint to 12.32 bits from 20.29 bits, the additional data comes from fonts and plugins.
It is also interesting to note that fingerprint scanners (fingerprints as on the ends of fingers) have false reject rates of about 0.5% and false acceptance rates of about 0.001%. Obviously they’re tuned that way to be 50x more likely to reject a legitimate user than to accept the wrong person and the algorithms are intrinsically fallible in both directions, so this is a necessary trade-off. Actual entropy measures in fingerprints are the subject of much debate. An estimate based on Pankanti‘s analysis computes a 5.5×10^59 chance of a collision or 193 bits of entropy but manufacturer published false acceptance rates of 0.001% are equivalent to 16.6 bits, less accurate than browser fingerprinting.