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>
    <allredirects garcontinue="Simulations_using_KPP-built_mechanisms" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1283" ns="0" title="Developing GEOS-Chem" />
      <page pageid="1073" ns="0" title="Emissions Working Group" />
      <page pageid="1641" ns="0" title="GEOS-Chem 12" />
      <page pageid="1642" ns="0" title="GEOS-Chem 12 benchmark history" />
      <page pageid="2076" ns="0" title="GEOS-Chem 13.0.0" />
      <page pageid="27" ns="0" title="GEOS-Chem Adjoint Model" />
      <page pageid="12" ns="0" title="GEOS-Chem versions" />
      <page pageid="1852" ns="0" title="Guide to using Git with GEOS-Chem" />
      <page pageid="934" ns="0" title="HEMCO data directories" />
      <page pageid="1575" ns="0" title="List of diagnostics archived to bpch format" />
    </pages>
  </query>
</api>