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="Marker_set-perspective_view-lowres.bmp|8" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="6" ns="6" title="File:Close Smile front view.jpg" />
      <f fromid="66" ns="6" title="File:EM-01 Aid Tray reference frame.jpg" />
      <f fromid="75" ns="6" title="File:EM-01 Aid Tray reference frame.jpg" />
      <f fromid="66" ns="6" title="File:EM-02 Coverplates Box reference frame.jpg" />
      <f fromid="75" ns="6" title="File:EM-02 Coverplates Box reference frame.jpg" />
      <f fromid="41" ns="6" title="File:Example frame atWork.png" />
      <f fromid="33" ns="6" title="File:FBM1 frames.zip" />
      <f fromid="5" ns="6" title="File:Footprint-RoCKIn-AtHome-2015-Rooms.png" />
      <f fromid="35" ns="6" title="File:Lexicon FBM3.zip" />
      <f fromid="75" ns="6" title="File:MarkerFBMArUco.pdf" />
    </allfileusages>
  </query>
</api>