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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.
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<?xml version="1.0"?>
<api>
  <query-continue>
    <allcategories accontinue="Augustan_wiki_training_templates" />
  </query-continue>
  <query>
    <allcategories>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">All pages needing cleanup</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki Lua templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki basic information</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki formatting and function templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki pages with incorrect protection templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki shortcut box first parameter needs fixing</c>
      <c size="3" pages="3" files="0" subcats="0" xml:space="preserve">Augustan Wiki soft redirected templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki training</c>
      <c size="4" pages="4" files="0" subcats="0" xml:space="preserve">Augustan Wiki training templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Augustan Wiki tutorials</c>
    </allcategories>
  </query>
</api>