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"?>
    <allfileusages gafcontinue="Cartoon_Milltaught.jpg" />
      <page pageid="1850" ns="6" title="File:Barrett CSR.pdf" />
      <page pageid="1584" ns="6" title="File:Bartsch AncientOptics.pdf" />
      <page pageid="1504" ns="6" title="File:Bluberries2.jpg" />
      <page pageid="1862" ns="6" title="File:BostromTranshumanismFAQ.pdf" />
      <page pageid="2859" ns="6" title="File:Brain size.png" />
      <page pageid="1537" ns="6" title="File:Bryant Savoring.pdf" />
      <page pageid="2137" ns="6" title="File:Cartoon54 Icouldcry.JPG" />
      <page pageid="2138" ns="6" title="File:Cartoon76Thedosage.JPG" />
      <page pageid="2139" ns="6" title="File:CartoonPaycut.jpg" />
      <page pageid="2134" ns="6" title="File:Cartoon Ivegotthebowl.jpg" />