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="BGhC8nX7_o.jpg|1336" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:B-02.jpg" />
      <f ns="6" title="File:B10hb-img600x450-1442681267cut0wj18813.jpg" />
      <f ns="6" title="File:B10hb-img600x450-1442681267pchttx18813.jpg" />
      <f ns="6" title="File:B10hb-img600x450-1442681267v6lg2518813.jpg" />
      <f ns="6" title="File:B459exmd4v2h2jk3k.jpg" />
      <f ns="6" title="File:B4706ca20b12896d4ff913961ad98f91 640 640.jpg" />
      <f ns="6" title="File:B8QvJ1cD o.jpg" />
      <f ns="6" title="File:B8xjJ.gif" />
      <f ns="6" title="File:BG-PC bg 1920 1080 EN.jpg" />
      <f ns="6" title="File:BG-iOS bg 1125 2436 EN.jpg" />
    </allfileusages>
  </query>
</api>