title: Is it possible to debug ExternalInterface through file:// from Flash Builder?
body: <p>I have a project written in ActionScript 3 using Adobe Flash Builder 4.5. It registers several functions in an <code>ExternalInterface</code>, so that they may be called from JavaScript.</p>
  
  <p>If I access the Flash document on a server, for example <code>http://localhost/</code>, I am able to call the defined functions successfully. If I just open the file in my browser directly (through the <code>file:///</code> protocol) it will fail with an error like this:</p>
  
  <pre><code>*** Security Sandbox Violation ***
  SecurityDomain 'null' tried to access incompatible context 'file:///Users/foo/src/bar/baz/bin-debug/app.swf'
  </code></pre>
  
  <p>A reasonable security restriction, but it has a paradoxical consequence: I'm unable to debug the use of <code>ExternalInterface</code> because the Flash Builder debugger opens the document through <code>file:</code>.</p>
  
  <p>It seems too absurd to be true that such an important feature can't be debugged normally.</p>
  
  <p>How can I use the debugger with <code>ExternalInterface</code>?</p>