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>
    <allpages apcontinue="Contao.Dev_ExtensionsBoxen" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="341" ns="0" title="BOM Checker" />
      <p pageid="357" ns="0" title="Back end Theme" />
      <p pageid="105" ns="0" title="Backend User Online" />
      <p pageid="117" ns="0" title="Banner" />
      <p pageid="118" ns="0" title="Banner Update v1 to v2" />
      <p pageid="22" ns="0" title="Beginner" />
      <p pageid="88" ns="0" title="Bot Detection" />
      <p pageid="691" ns="0" title="Bot Statistic" />
      <p pageid="9" ns="0" title="Chat HowTo" />
      <p pageid="210" ns="0" title="Code Styleguide" />
    </allpages>
  </query>
</api>