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>
    <pages>
      <page pageid="4" ns="0" title="Inleiding en participatie" />
      <page pageid="5" ns="0" title="Spangen, Oud-Mathenesse en Witte Dorp" />
      <page pageid="6" ns="0" title="Bospolder-Tussendijken" />
      <page pageid="7" ns="0" title="Middelland en het Nieuwe Westen" />
      <page pageid="8" ns="0" title="Delfshaven, Schiemond en het Lloydkwartier" />
      <page pageid="23" ns="0" title="Tekstopmaak opties" />
      <page pageid="25" ns="0" title="Participatiebudget en &#039;Open Spending&#039;" />
      <page pageid="33" ns="0" title="Adviesnota&#039;s" />
      <page pageid="604" ns="0" title="Tatarnikov Alexander (diezel sun)" />
    </pages>
  </query>
</api>