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 aistart="2018-04-25T12:38:44Z" />
  </query-continue>
  <query>
    <allimages>
      <img name="OpenCellID_banner_links2.png" timestamp="2018-04-25T13:45:52Z" user="Admin" url="http://wiki.opencellid.org/images/5/58/OpenCellID_banner_links2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_links2.png" ns="6" title="File:OpenCellID banner links2.png" />
      <img name="OpenCellID_banner_antennas2.png" timestamp="2018-04-25T13:43:04Z" user="Admin" url="http://wiki.opencellid.org/images/6/61/OpenCellID_banner_antennas2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_antennas2.png" ns="6" title="File:OpenCellID banner antennas2.png" />
      <img name="OpenCellID_banner_history2.png" timestamp="2018-04-25T13:39:50Z" user="Admin" url="http://wiki.opencellid.org/images/3/34/OpenCellID_banner_history2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_history2.png" ns="6" title="File:OpenCellID banner history2.png" />
      <img name="OpenCellID_banner_FAQ2.png" timestamp="2018-04-25T13:34:20Z" user="Admin" url="http://wiki.opencellid.org/images/1/18/OpenCellID_banner_FAQ2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_FAQ2.png" ns="6" title="File:OpenCellID banner FAQ2.png" />
      <img name="OpenCellID_banner_3_antennas-022.png" timestamp="2018-04-25T13:25:54Z" user="Admin" url="http://wiki.opencellid.org/images/c/ce/OpenCellID_banner_3_antennas-022.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_3_antennas-022.png" ns="6" title="File:OpenCellID banner 3 antennas-022.png" />
      <img name="OpenCellID_banner_licensing2.png" timestamp="2018-04-25T13:17:49Z" user="Admin" url="http://wiki.opencellid.org/images/4/48/OpenCellID_banner_licensing2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_licensing2.png" ns="6" title="File:OpenCellID banner licensing2.png" />
      <img name="OpenCellID_banner_statistics2.png" timestamp="2018-04-25T13:15:03Z" user="Admin" url="http://wiki.opencellid.org/images/2/26/OpenCellID_banner_statistics2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_statistics2.png" ns="6" title="File:OpenCellID banner statistics2.png" />
      <img name="OpenCellID_banner_upload2.png" timestamp="2018-04-25T13:10:30Z" user="Admin" url="http://wiki.opencellid.org/images/9/9b/OpenCellID_banner_upload2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_banner_upload2.png" ns="6" title="File:OpenCellID banner upload2.png" />
      <img name="OpenCellID_I_want_to_use_the_data2.png" timestamp="2018-04-25T12:43:54Z" user="Admin" url="http://wiki.opencellid.org/images/2/2d/OpenCellID_I_want_to_use_the_data2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_I_want_to_use_the_data2.png" ns="6" title="File:OpenCellID I want to use the data2.png" />
      <img name="OpenCellID_scoring_lists2.png" timestamp="2018-04-25T12:38:54Z" user="Admin" url="http://wiki.opencellid.org/images/c/c0/OpenCellID_scoring_lists2.png" descriptionurl="http://wiki.opencellid.org/wiki/File:OpenCellID_scoring_lists2.png" ns="6" title="File:OpenCellID scoring lists2.png" />
    </allimages>
  </query>
</api>