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>
    <allfileusages gafcontinue="Bau_Prades,_Calasanz-v01n01.jpg|6875" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6839" ns="0" title="Tomás Báguena" />
      <page pageid="6841" ns="0" title="Miquel Balagué Salvia" />
      <page pageid="6843" ns="0" title="György Balanyi" />
      <page pageid="6866" ns="0" title="Eugenio Barsanti" />
      <page pageid="6873" ns="0" title="Jòzsef Bátori" />
      <page pageid="13135" ns="0" title="Francesco Barberini" />
      <page pageid="13137" ns="0" title="József Batthyány" />
      <page pageid="13598" ns="0" title="Barbastro (ES) Colegio San Lorenzo" />
      <page pageid="13611" ns="0" title="Barcelona (ES) Real colegio Escuelas Pías de Sarria" />
    </pages>
  </query>
</api>