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="Benajmin.jpg" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Backpack diagram.jpg" />
      <f ns="6" title="File:Backpack straps.jpg" />
      <f ns="6" title="File:Bathroom Door 3D.jpg" />
      <f ns="6" title="File:Bathroom Eye Count 3D.jpg" />
      <f ns="6" title="File:Bathroom From Interlock 3D.jpg" />
      <f ns="6" title="File:Bathroom Looking Into Interlock 3D.jpg" />
      <f ns="6" title="File:Bathroom Wall 3D.jpg" />
      <f ns="6" title="File:Bees.png" />
      <f ns="6" title="File:Ben nun.jpg" />
      <f ns="6" title="File:Ben paul.JPG" />
    </allfileusages>
  </query>
</api>