title: JMeter - Why sending default User-Agent header
body: <p>When sending HTTP Request in JMeter, User-Agent header is added,e.g.:</p>
  
  <blockquote>
    <p>User-Agent: Apache-HttpClient/4.5.10 (Java/1.8.0_191)
    Content-Type: text/plain
    Host: api.example.com</p>
  </blockquote>
  
  <p>I didn't find any reason in documentation, </p>
  
  <p>But there's a reference to its existence in <a href="http://jmeter.apache.org/usermanual/component_reference.html#HTTP_Header_Manager" rel="nofollow noreferrer">JMeter docs</a></p>
  
  <blockquote>
    <p>In this example, we created a Test Plan that tells JMeter to override the default "User-Agent" request header and use a particular Internet Explorer agent string instead.</p>
  </blockquote>
  
  <p>When changing to Java in Advanced -> Implementation it doesn't send extra headers, so it's related to <a href="http://jmeter.apache.org/usermanual/component_reference.html#HTTP_Header_Manager" rel="nofollow noreferrer">HTTPClient4</a></p>
  
  <blockquote>
    <p>HttpClient sends a default User-Agent header with every request</p>
  </blockquote>
  
  <p>But what is the reason behind it? </p>
  
  <p>Also when I try to remove it, by adding User-Agent with empty value in Header Manager</p>
  
  <p>Still it sends User-Agent with empty value, is there a way to avoid sending User-Agent header?</p>
  
  <ul>
  <li>Note in cUrl you can <a href="https://stackoverflow.com/questions/31293181/how-can-i-remove-default-headers-that-curl-sends">remove default User-Agent</a> using <code>curl --verbose -H 'User-Agent:'</code></li>
  </ul>