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>
    <recentchanges>
      <rc type="edit" ns="0" title="Portal development frontend" pageid="318" revid="3561" old_revid="3560" rcid="3579" timestamp="2018-12-20T11:02:55Z" />
      <rc type="edit" ns="0" title="Portal development frontend" pageid="318" revid="3560" old_revid="3459" rcid="3578" timestamp="2018-12-20T10:51:46Z" />
      <rc type="log" ns="6" title="File:Sviluppo prtale Addendum.pdf" pageid="444" revid="0" old_revid="0" rcid="3577" timestamp="2018-12-20T10:31:00Z" />
      <rc type="log" ns="6" title="File:Sviluppo portale Flusso.pdf" pageid="443" revid="0" old_revid="0" rcid="3576" timestamp="2018-12-20T10:30:27Z" />
      <rc type="log" ns="6" title="File:Utenti widget uso 30 12 2016.pdf" pageid="442" revid="0" old_revid="0" rcid="3575" timestamp="2018-12-20T10:27:57Z" />
      <rc type="new" ns="0" title="Open access" pageid="441" revid="3556" old_revid="0" rcid="3574" timestamp="2017-09-26T13:48:39Z" />
      <rc type="edit" ns="0" title="API" pageid="439" revid="3555" old_revid="3553" rcid="3573" timestamp="2017-09-26T10:10:16Z" />
      <rc type="new" ns="0" title="CRIS" pageid="440" revid="3554" old_revid="0" rcid="3572" timestamp="2017-09-26T10:00:03Z" />
      <rc type="new" ns="0" title="API" pageid="439" revid="3553" old_revid="0" rcid="3571" timestamp="2017-09-26T09:36:17Z" />
    </recentchanges>
  </query>
</api>