Go between M-IDs and filenames on Wikimedia Commons

• Posted 8 December 2023
• Tagged with wikimedia-commons

Every file on Wikimedia Commons has two identifiers:

• A filename, e.g. File:Herestraat Groningen.JPG. This always starts with File: because these are pages in the File namespace
• A numeric identifier, e.g. M128. This is a unique identifier for each file on Commons, similar to Q IDs for entities on Wikidata.

The APIs for searching/updating Wikimedia Commons typically accept both forms; sometimes it’s convenient to go between the two.

1. To go from filename to numeric ID, you can use the Query API and do a search with the titles parameter. The M ID is included in the response.

   For example:

   curl \
     --get 'https://commons.wikimedia.org/w/api.php' \
     --data 'action=query' \
     --data 'format=xml' \
     --data-urlencode 'titles=File:Herestraat Groningen.JPG'
   

   <api batchcomplete="">
     <query>
       <pages>
         <page _idx="128" pageid="128" ns="6" title="File:Herestraat Groningen.JPG"/>
       </pages>
     </query>
   </api>
   

2. To go from numeric ID to filename, go to https://commons.wikimedia.org/?curid=[ID].

   For example, https://commons.wikimedia.org/?curid=128.

   Alternatively, you can use the Query API with the pageids parameter. For example:

   curl \
     --get 'https://commons.wikimedia.org/w/api.php' \
     --data 'action=query' \
     --data 'format=xml' \
     --data 'pageids-128'
   

   <?xml version="1.0"?>
   <api batchcomplete="">
     <query>
       <pages>
         <page _idx="128" pageid="128" ns="6" title="File:Herestraat Groningen.JPG"/>
       </pages>
     </query>
   </api>
   

There’s a Python implementation of this code in Flickypedia, which includes some tests.