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="Rory_intro_colored_02.jpg|31" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="35" ns="6" title="File:Cancunchyk.jpg" />
      <f fromid="12" ns="6" title="File:Erminig - May 2014.jpg" />
      <f fromid="30" ns="6" title="File:Erminig - May 2014.jpg" />
      <f fromid="33" ns="6" title="File:Erminig avec un sous-bock Wikipédia.jpg" />
      <f fromid="18" ns="6" title="File:Henry, Peter the WikiPlaytpus and friend.jpg" />
      <f fromid="1" ns="6" title="File:Les peluches font du géocaching - Toulouse.jpg" />
      <f fromid="7" ns="6" title="File:Percy, répondeur téléphonique, Wikimédia France.jpg" />
      <f fromid="12" ns="6" title="File:Percy, répondeur téléphonique, Wikimédia France.jpg" />
      <f fromid="5" ns="6" title="File:Petit tigre on the top of Manhattan.jpg" />
      <f fromid="12" ns="6" title="File:Petit tigre on the top of Manhattan.jpg" />
    </allfileusages>
  </query>
</api>