Hello all,
Is it possible through api to know all characters wearing a certain item ?
Thx for answering 
If you mean all of your characters or all characters form a specific guild, then yes, it is doable, but you’ll have to implement your own script/database for that and iterate over each character/member to fetch equipment information and filter the item.
If you mean ALL characters from the entire WoW universe then of course not.
Thx Schiller for answering, i fact, yes for an entire realm it would have been cool 
But ok for a specific guild !