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">Media</ns>
      <ns id="-1" case="first-letter" canonical="Special" xml:space="preserve">Special</ns>
      <ns id="0" case="first-letter" content="" xml:space="preserve" />
      <ns id="1" case="first-letter" subpages="" canonical="Talk" xml:space="preserve">Talk</ns>
      <ns id="2" case="first-letter" subpages="" canonical="User" xml:space="preserve">User</ns>
      <ns id="3" case="first-letter" subpages="" canonical="User talk" xml:space="preserve">User talk</ns>
      <ns id="4" case="first-letter" subpages="" canonical="Project" xml:space="preserve">Global wiki. Wargaming.net</ns>
      <ns id="5" case="first-letter" subpages="" canonical="Project talk" xml:space="preserve">Global wiki. Wargaming.net talk</ns>
      <ns id="6" case="first-letter" canonical="File" xml:space="preserve">File</ns>
      <ns id="7" case="first-letter" subpages="" canonical="File talk" xml:space="preserve">File talk</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 talk</ns>
      <ns id="10" case="first-letter" canonical="Template" xml:space="preserve">Template</ns>
      <ns id="11" case="first-letter" subpages="" canonical="Template talk" xml:space="preserve">Template talk</ns>
      <ns id="12" case="first-letter" subpages="" canonical="Help" xml:space="preserve">Help</ns>
      <ns id="13" case="first-letter" subpages="" canonical="Help talk" xml:space="preserve">Help talk</ns>
      <ns id="14" case="first-letter" canonical="Category" xml:space="preserve">Category</ns>
      <ns id="15" case="first-letter" subpages="" canonical="Category talk" xml:space="preserve">Category talk</ns>
      <ns id="10000" case="first-letter" canonical="Tank" content="" xml:space="preserve">Tank</ns>
      <ns id="10001" case="first-letter" canonical="Tank talk" xml:space="preserve">Tank talk</ns>
      <ns id="10002" case="first-letter" canonical="Plane" content="" xml:space="preserve">Plane</ns>
      <ns id="10003" case="first-letter" canonical="Plane talk" xml:space="preserve">Plane talk</ns>
      <ns id="10004" case="first-letter" canonical="Ship" content="" xml:space="preserve">Ship</ns>
      <ns id="10005" case="first-letter" canonical="Ship talk" xml:space="preserve">Ship talk</ns>
      <ns id="10006" case="first-letter" canonical="Card" content="" xml:space="preserve">Card</ns>
      <ns id="10007" case="first-letter" canonical="Card talk" xml:space="preserve">Card talk</ns>
      <ns id="10008" case="first-letter" canonical="Navy" content="" xml:space="preserve">Navy</ns>
      <ns id="10009" case="first-letter" canonical="Navy talk" xml:space="preserve">Navy talk</ns>
      <ns id="10010" case="first-letter" canonical="Blitz" content="" xml:space="preserve">Blitz</ns>
      <ns id="10011" case="first-letter" canonical="Blitz talk" xml:space="preserve">Blitz talk</ns>
      <ns id="10012" case="first-letter" canonical="XBOX" content="" xml:space="preserve">XBOX</ns>
      <ns id="10013" case="first-letter" canonical="XBOX talk" xml:space="preserve">XBOX talk</ns>
      <ns id="10014" case="first-letter" canonical="TWA" content="" xml:space="preserve">TWA</ns>
      <ns id="10015" case="first-letter" canonical="TWA talk" xml:space="preserve">TWA talk</ns>
      <ns id="10016" case="first-letter" canonical="Antiquity" content="" xml:space="preserve">Antiquity</ns>
      <ns id="10017" case="first-letter" canonical="Antiquity talk" xml:space="preserve">Antiquity talk</ns>
      <ns id="10018" case="first-letter" canonical="Caliber" content="" xml:space="preserve">Caliber</ns>
      <ns id="10019" case="first-letter" canonical="Caliber talk" xml:space="preserve">Caliber talk</ns>
      <ns id="10020" case="first-letter" canonical="SpecOps" content="" xml:space="preserve">SpecOps</ns>
      <ns id="10021" case="first-letter" canonical="SpecOps talk" xml:space="preserve">SpecOps talk</ns>
    </namespaces>
  </query>
</api>