c69's Browser Pit

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There is a mathematical quantity which allows us to measure how close a fact comes to revealing somebody's identity uniquely. That quantity is called entropy, and it's often measured in bits.
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Because there are around 7 billion humans on the planet, the identity of a random, unknown person contains just under 33 bits of entropy (two to the power of 33 is 8 billion). When we learn a new fact about a person, that fact reduces the entropy of their identity by a certain amount.
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So for instance, if we know someone's birthday, and we know their ZIP code is 40203, we have 8.51 + 23.81 = 32.32 bits; that's almost, but perhaps not quite, enough to know who they are: there might be a couple of people who share those characteristics. Add in their gender, that's 33.32 bits, and we can probably say exactly who the person is.

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Now, how would this paradigm apply to web browsers? It turns out that, in addition to the commonly discussed "identifying" characteristics of web browsers, like IP addresses and tracking cookies, there are more subtle differences between browsers that can be used to tell them apart.

One significant example is the User-Agent string, which contains the name, operating system and precise version number of the browser, and which is sent every web server you visit.

As a part of Microsoft’s continued commitment to interoperability and standards support, yesterday we submitted our request to join the Scalable Vector Graphics (SVG) Working Group of the World Wide Web Consortium (W3C). We’re excited to take part in ensuring future versions of the SVG spec will meet the needs of developers and end users.