<p>There is enough information in the user agent that sometimes only a few visitors to a website will be the same. If the user agent is combined with another piece of non-unique identifying information, often it results in a unique fingerprint.
The Electronic Frontier Foundation created a tool called <a href="https://panopticlick.eff.org/">Panopticlick</a> to demonstrate how much information can be gleaned from these sources. If this test is run with JavaScript enabled the
amount of information that is disclosed increases greatly. <a href="https://www.browserleaks.com">Browser Leaks</a> and <a href="https://amiunique.org/">Am I Unique</a> are also good sources of information.</p>
<p>There is enough information in the user agent that sometimes only a few visitors to a website will be the same. If the user agent is combined with another piece of non-unique identifying information, often it results in a unique fingerprint.
The Electronic Frontier Foundation created a tool called <a href="https://panopticlick.eff.org/">Panopticlick</a> to demonstrate how much information can be gleaned from these sources. If this test is run with JavaScript enabled the
amount of information that is disclosed increases greatly. <a href="https://www.browserleaks.com">Browser Leaks</a> and <a href="https://amiunique.org/">Am I Unique</a> are also good sources of information.</p>