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>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="MediaWiki default" anon="" comment="" />
        </revisions>
      </page>
    </pages>
    <general mainpage="Hauptseite" base="http://hillebrand.de/index.php?title=Hauptseite" sitename="Familienalbum" logo="" generator="MediaWiki 1.23.14" phpversion="8.2.18" phpsapi="cgi-fcgi" dbtype="mysql" dbversion="5.7.42-log" imagewhitelistenabled="" langconversion="" titleconversion="" linkprefixcharset="" linkprefix="" linktrail="/^([äöüßa-z]+)(.*)$/sDu" case="first-letter" lang="de" fallback8bitEncoding="windows-1252" readonly="" readonlyreason="This wiki is currently being upgraded to a newer software version." writeapi="" timezone="UTC" timeoffset="0" articlepath="/index.php?title=$1" scriptpath="" script="/index.php" server="http://hillebrand.de" wikiid="DB2807154" time="2024-04-27T08:51:47Z" maxuploadsize="104857600" minuploadchunksize="1024" favicon="http://hillebrand.de/favicon.ico">
      <fallback>
        <lang code="en" />
      </fallback>
      <thumblimits>
        <limit>120</limit>
        <limit>150</limit>
        <limit>180</limit>
        <limit>200</limit>
        <limit>250</limit>
        <limit>300</limit>
      </thumblimits>
      <imagelimits>
        <limit width="320" height="240" />
        <limit width="640" height="480" />
        <limit width="800" height="600" />
        <limit width="1024" height="768" />
        <limit width="1280" height="1024" />
      </imagelimits>
    </general>
  </query>
</api>