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="BeerWorm_Gameplay_screen.png" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BOFH Servers Under Siege C64 Gameplay screen.png" />
      <f ns="6" title="File:BOFH Servers Under Siege C64 Title screen.png" />
      <f ns="6" title="File:BOFH Servers Under Siege PC Gameplay screen.png" />
      <f ns="6" title="File:BOFH Servers Under Siege PC Title screen.png" />
      <f ns="6" title="File:Bad Road (Apogee BK-01) Gameplay screen.png" />
      <f ns="6" title="File:Ballo Gameplay screen.jpg" />
      <f ns="6" title="File:Barely Floating Gameplay screen.jpg" />
      <f ns="6" title="File:Barely Floating Main menu.jpg" />
      <f ns="6" title="File:Basic-kaantaja Cover.jpg" />
      <f ns="6" title="File:Bazooka-Assault Trooper item.png" />
    </allfileusages>
  </query>
</api>