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>
    <allimages gaicontinue="600px-Gentoo26c3.jpeg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2756" ns="6" title="File:05-femlogoname-blau-91 height.gif" />
      <page pageid="2791" ns="6" title="File:151126 lightning talk 32C3.pdf" />
      <page pageid="3034" ns="6" title="File:20151224 001.jpg" />
      <page pageid="3035" ns="6" title="File:20151224 003.jpg" />
      <page pageid="2281" ns="6" title="File:318px-Sandbox with interactive projection at 31c3.jpg" />
      <page pageid="2924" ns="6" title="File:32c3-sim-back.jpg" />
      <page pageid="2923" ns="6" title="File:32c3-sim-front.jpg" />
      <page pageid="2558" ns="6" title="File:32c3-track-colors-desaturated.png" />
      <page pageid="2551" ns="6" title="File:32c3-track-colors.png" />
      <page pageid="2594" ns="6" title="File:450px-Kombucha mother burdger view kasiri south korea 1600 1200 fa20052013.jpg" />
    </pages>
  </query>
</api>