You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information.
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages afcontinue="Barbarian_on_battlefield.gif" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Back For Revenge (Allies) map large.png" />
      <f ns="6" title="File:Back For Revenge map large.png" />
      <f ns="6" title="File:Badge of Courage artifact.gif" />
      <f ns="6" title="File:Ballista.png" />
      <f ns="6" title="File:Ballista portrait.gif" />
      <f ns="6" title="File:Barbarian Breakout (Allies) map large.png" />
      <f ns="6" title="File:Barbarian Breakout (Allies) underground map large.png" />
      <f ns="6" title="File:Barbarian Breakout map large.png" />
      <f ns="6" title="File:Barbarian Breakout underground map large.png" />
      <f ns="6" title="File:Barbarian Lord&#039;s Axe of Ferocity.gif" />
    </allfileusages>
  </query>
</api>