Configure Entity Tags (ETags)

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If you have ever used the YSlow (http://developer.yahoo.com/yslow/) to analyze the web page to improve the performance, you may have experienced with “Configure ETags” alert.

YSlow Analyse

What is Entity Tags (ETags)

Entity tags (ETags) are a mechanism web servers and the browser use to determine whether a component in the browser’s cache matches one on the origin server. Since ETags are typically constructed using attributes that make them unique to a specific server hosting a site, the tags will not match when a browser gets the original component from one server and later tries to validate that component on a different server. (http://developer.yahoo.com/performance/rules.html#etags)

“Configure ETags” is a recommended best practices for speeding up the web site. If you are an ASP.NET developer, you can configure this by adding following code to the web.config file.

<system.webServer>
  <httpProtocol>
    <customHeaders>
      <clear/>
      <add name="ETag" value=" "/>
    </customHeaders>
  </httpProtocol>
</system.webServer>