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>
    <alllinks galcontinue="Bloc_de_constitutionnalité" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Basque" missing="" />
      <page ns="0" title="Bağış" missing="" />
      <page ns="0" title="Before" missing="" />
      <page ns="0" title="Behold" missing="" />
      <page ns="0" title="Besien" missing="" />
      <page ns="0" title="Bg:Шаблон:Скриване" missing="" />
      <page ns="0" title="Bg:Шаблон:Шахматна позиция" missing="" />
      <page ns="0" title="Biri" missing="" />
      <page ns="0" title="Bishop" missing="" />
      <page pageid="263" ns="0" title="BRH 82 du 1er septembre 2004" />
    </pages>
  </query>
</api>