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="Context_icon_burn.png" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Bunny carrying items1.jpg" />
      <f ns="6" title="File:C sign.jpg" />
      <f ns="6" title="File:Communitymap BraveBunny Tiled.png" />
      <f ns="6" title="File:Communitymap RocksPlayground Tiled.png" />
      <f ns="6" title="File:Communitymap ZoneSix Tiled.png" />
      <f ns="6" title="File:Communitymap madeIn30Minutes Tiled.png" />
      <f ns="6" title="File:Communitymap palace Tiled.png" />
      <f ns="6" title="File:Communitymap zoneFive Tiled.png" />
      <f ns="6" title="File:Concept art bunny01.jpg" />
      <f ns="6" title="File:Context icon alert.png" />
    </allfileusages>
  </query>
</api>