title: Correct way to pass multiple values for same parameter name in GET request
body: <p>I'm looking into what is the correct way to pass multiple values for the same parameter name in a GET request.</p>
  
  <p>I've seen URLs like this:</p>
  
  <pre><code>http://server/action?id=a&amp;id=b
  </code></pre>
  
  <p>And I've seen URLs like this:</p>
  
  <pre><code>http://server/action?id=a,b
  </code></pre>
  
  <p>My understanding is that the first is correct, but I can't find any reference for this. I had a look at the http spec but couldn't see anything about how the 'query' part of a URL should be made up.</p>
  
  <p>I don't want an answer that says "either is fine" - if I'm building a webservice, I want to know which of these methods is standard so that people using my webservice know how to pass multiple parameters for the same name.</p>
  
  <p>So, can someone point me at an official reference source to confirm which option is correct?</p>