title: How do you determine what technology a website is built on?
body: <p>Quite often I come across a nice looking or functional website, and wonder what technology was used to create it. What techniques are available to figure out what a
  particular website was built with?</p>
  
  <p>Few frameworks seem to include any kind of generator meta tag like web editors do. Are there any tell-tale signs of particular languages and/or frameworks?</p>
  
  <hr>
  
  <p><strong><em>Summary of answers</em></strong></p>
  
  <p>Site URLs may betray the framework and/or programming language but cannot be relied upon (e.g. file extensions such as .asp). HTTP response headers, cookies, stylesheets and source comments may also give clues.</p>
  
  <p>Some nice tools for querying site details (no doubt there are many more):</p>
  
  <ul>
  <li><a href="http://builtwith.com/" rel="noreferrer">BuiltWith</a></li>
  <li><a href="http://www.domaintools.com/" rel="noreferrer">DomainTools</a></li>
  <li><a href="http://news.netcraft.com/" rel="noreferrer">NetCraft</a></li>
  <li><a href="http://w3techs.com/sites" rel="noreferrer">W3Techs</a></li>
  <li><a href="http://www.similartech.com" rel="noreferrer">SimilarTech</a></li>
  </ul>
  
  <p>Firefox addons:</p>
  
  <ul>
  <li><a href="http://wappalyzer.com/" rel="noreferrer">Wappalyzer</a> - CMS, frameworks/libraries, e-commerce, message boards etc.</li>
  <li><a href="https://addons.mozilla.org/en-US/firefox/addon/2166" rel="noreferrer">Domain Details</a> - IP, country and webserver details</li>
  <li><a href="https://addons.mozilla.org/en-US/firefox/addon/10083" rel="noreferrer">Library Detector</a> - Javascript libraries in use</li>
  </ul>
  
  <p>Chrome Extensions:</p>
  
  <ul>
  <li><a href="http://wappalyzer.com/" rel="noreferrer">Wappalyzer</a></li>
  <li><a href="https://chrome.google.com/webstore/detail/similartech-site-technolo/jiabgmelnfhgjkfdaoiccfcbaedjfcnm" rel="noreferrer">SimilarTech</a></li>
  <li><a href="https://chrome.google.com/webstore/detail/pagexray/aedmpdookgbneegaeajpoldpnpfbpmlb" rel="noreferrer">PageXray</a></li>
  </ul>
  
  <p>Bookmarklets:</p>
  
  <ul>
  <li><a href="http://blog.olicio.us/2008/11/08/wtframework-bookmarklet/" rel="noreferrer">WTFramework</a> - shows Javascript framework in use</li>
  </ul>