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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.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <messagegroups>
      <group id="page-Colorduino V1.4" label="Colorduino V1.4" description="Translation of the wiki page [[:Colorduino V1.4|Colorduino V1.4]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-IR Shield" label="IR Shield" description="Translation of the wiki page [[:IR Shield|IR Shield]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-ITDB02-1.8SP" label="ITDB02-1.8SP" description="Translation of the wiki page [[:ITDB02-1.8SP|ITDB02-1.8SP]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-ITDB02-2.2S" label="ITDB02-2.2S" description="Translation of the wiki page [[:ITDB02-2.2S|ITDB02-2.2S]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-ITDB02-2.4S" label="ITDB02-2.4S" description="Translation of the wiki page [[:ITDB02-2.4S|ITDB02-2.4S]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-ITDB02-2.8" label="ITDB02-2.8" description="Translation of the wiki page [[:ITDB02-2.8|ITDB02-2.8]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-Main Page" label="Main Page" description="Translation of the wiki page [[:Main Page|Main Page]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-Mini Rboard" label="Mini Rboard" description="Translation of the wiki page [[:Mini Rboard|Mini Rboard]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-Nextion HMI Solution" label="Nextion HMI Solution" description="Translation of the wiki page [[:Nextion HMI Solution|Nextion HMI Solution]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-RASPBERRY PI Arduino Shield ADD-ON" label="RASPBERRY PI Arduino Shield ADD-ON" description="Translation of the wiki page [[:RASPBERRY PI Arduino Shield ADD-ON|RASPBERRY PI Arduino Shield ADD-ON]]." class="WikiPageMessageGroup" exists="" />
      <group id="page-RASPBERRY PI OLED ADD-ON" label="RASPBERRY PI OLED ADD-ON" description="Translation of the wiki page [[:RASPBERRY PI OLED ADD-ON|RASPBERRY PI OLED ADD-ON]]." class="WikiPageMessageGroup" exists="" />
      <group id="!additions" label="Recent additions" description="This message group shows new and changed messages." class="RecentAdditionsMessageGroup" exists="" />
      <group id="!recent" label="Recent translations" description="This message group shows all recent translations into this language.&#10;Most useful for the review tasks." class="RecentMessageGroup" exists="" />
      <group id="!sandbox" label="Sandbox messages" description="Suggests messages to translate for sandboxed users" class="SandboxMessageGroup" exists="" />
      <group id="wiki-sidebar" label="Sidebar" description="Messages used in the sidebar of this wiki" class="WikiMessageGroup" exists="" />
    </messagegroups>
  </query>
</api>