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>
    <namespaces>
      <ns id="-2" case="first-letter" canonical="Media" xml:space="preserve">Medium</ns>
      <ns id="-1" case="first-letter" canonical="Special" xml:space="preserve">Spezial</ns>
      <ns id="0" case="first-letter" content="" xml:space="preserve" />
      <ns id="1" case="first-letter" subpages="" canonical="Talk" xml:space="preserve">Diskussion</ns>
      <ns id="2" case="first-letter" subpages="" canonical="User" xml:space="preserve">Benutzer</ns>
      <ns id="3" case="first-letter" subpages="" canonical="User talk" xml:space="preserve">Benutzer Diskussion</ns>
      <ns id="4" case="first-letter" subpages="" canonical="Project" xml:space="preserve">U-Boot-Archiv Wiki</ns>
      <ns id="5" case="first-letter" subpages="" canonical="Project talk" xml:space="preserve">U-Boot-Archiv Wiki Diskussion</ns>
      <ns id="6" case="first-letter" canonical="File" xml:space="preserve">Datei</ns>
      <ns id="7" case="first-letter" subpages="" canonical="File talk" xml:space="preserve">Datei Diskussion</ns>
      <ns id="8" case="first-letter" subpages="" canonical="MediaWiki" xml:space="preserve">MediaWiki</ns>
      <ns id="9" case="first-letter" subpages="" canonical="MediaWiki talk" xml:space="preserve">MediaWiki Diskussion</ns>
      <ns id="10" case="first-letter" canonical="Template" xml:space="preserve">Vorlage</ns>
      <ns id="11" case="first-letter" subpages="" canonical="Template talk" xml:space="preserve">Vorlage Diskussion</ns>
      <ns id="12" case="first-letter" subpages="" canonical="Help" xml:space="preserve">Hilfe</ns>
      <ns id="13" case="first-letter" subpages="" canonical="Help talk" xml:space="preserve">Hilfe Diskussion</ns>
      <ns id="14" case="first-letter" canonical="Category" xml:space="preserve">Kategorie</ns>
      <ns id="15" case="first-letter" subpages="" canonical="Category talk" xml:space="preserve">Kategorie Diskussion</ns>
    </namespaces>
  </query>
</api>