This change only affects clients using the JSON, PHP, WDDX, PHP, TXT and DBG formats. If you're using the XML or YAML formats, nothing will change for you. The list=backlinks, list=embeddedin and list=imageusage used to return arrays with pageIDs as keys, duplicating information (those arrays also contain the pageID). An example (in JSON): { "query": { "backlinks": { "1024": { "pageid": "1024", "ns": 1, "title": "Talk:Anarcho-capitalism" }, "1236": { "pageid": "1236", "ns": 1, "title": "Talk:Algorithm" } } } } After a complaint [1] about this behavior, it was changed in r39645 [2]. Like all other list= modules, backlinks and friends now return arrays with 0, 1, 2, etc. as keys. In JSON this looks like: { "query": { "backlinks": [ { "pageid": "1024", "ns": 1, "title": "Talk:Anarcho-capitalism" }, { "pageid": "1236", "ns": 1, "title": "Talk:Algorithm" } ] } } Roan Kattouw (Catrope) [1] http://lists.wikimedia.org/pipermail/mediawiki-api/2008-August/000657.html [2] http://svn.wikimedia.org/viewvc/mediawiki?view=rev&revision=39645