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="Barcelona_Cavalry_Regimental_Standard.jpg" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Baaden Infantry Grenadier Mitre Cap.jpg" />
      <f ns="6" title="File:Baaden Infantry Uniform Plate.jpg" />
      <f ns="6" title="File:Baden-Baden Infantry Uniform Plate 1762.jpg" />
      <f ns="6" title="File:Baden-Durlach Infantry Private.jpg" />
      <f ns="6" title="File:Baden-Durlach Infantry Uniform Plate 1762.jpg" />
      <f ns="6" title="File:Baguettes Punishment.jpg" />
      <f ns="6" title="File:Banal-Grenzinfanterieregiment nr. 1 Uniform Plate.jpg" />
      <f ns="6" title="File:Banal-Grenzinfanterieregiment nr. 2 Uniform Plate.jpg" />
      <f ns="6" title="File:Banater Grenz-Hussars Uniform Plate 1762.jpg" />
      <f ns="6" title="File:Baranyay Hussars Uniform Plate 1757.jpg" />
    </allfileusages>
  </query>
</api>