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 gafcontinue="Bear-tracks.svg|1666" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1626" ns="0" title="Frieze Patterns" />
      <page pageid="1969" ns="0" title="Depth and Perspective" />
      <page pageid="1970" ns="0" title="The Fourth Dimension" />
      <page pageid="2063" ns="0" title="The Mobius Band and Other Surfaces" />
      <page pageid="2064" ns="0" title="Möbius Strip Exploration" />
      <page pageid="2885" ns="0" title="Bat Pattern (Satin)" />
      <page pageid="2905" ns="0" title="Rotational Symmetry" />
      <page pageid="3332" ns="0" title="Balcony" />
      <page pageid="3802" ns="0" title="Escher Artwork Gallery" />
    </pages>
  </query>
</api>