(Maybe I should add that I'm a biologist, so its mainly journal references that I'm talking about, and in the context of writing my own manuscripts etc.)

Thanks for you reply.
Yes, next to identical at least - and since I have so many of them anyway I'm not going to bother choosing one over the other, a simple merge using the newest item as "master" would suffice.

If there isnt a way to get a solution to this I will basically have to choose one of my libraries and discard all of the others, since there is a big overlap. It also prevents me from searching on ISI for a topic/organism/method/etc I'm currently interested in and writing about, downloading all the citations and then putting them into my library. Because that would in almost all cases lead to a huge amount of duplicates...

Actually, simply deleting the oldest duplicate would be perfectly fine too, if merging is intensive computationally.

I tried following your advice, but I dont see how this would allow me to delete *only* the duplicates imported at the time, and not all the references imported at that time? Or do you mean I have to add the "duplicate" tag to all duplicate items? Because that kinda defeats the purpose of not having to click "merge" a thousand times in the duplicates list..

I found a "solution" by installing endnote in trial mode, exporting the zotero library to RIS, importing the RIS file into endnote and chose the "remove duplicates" when prompted in the import sequence. But then I'm left wondering if I should just stick with endnote instead... although I dont particularly like it.

This is a quick and dirty hack for automating the merger of duplicate zotero items.
In order to use this you will need to have your zotero library open in firefox and have a set of duplicate items selected in the duplicate pane.

Open a browser tab and enter: chrome://zotero/content/include.js


Then open the "Web Console" from the developer tools(there are other options like Execute JS too)


Then paste the following lines into the console:


var Zot_Dup_Pane = Components.classes["@mozilla.org/appshell/window-mediator;1"] .getService(Components.interfaces.nsIWindowMediator).getMostRecentWindow("navigator:browser").Zotero_Duplicates_Pane;


//note this will fail on duplicates that are not the same item type or it may crash if you have a large library - in which case I export subsections of the
//library and merge them in smaller sets - importing them into a new library at the end.
//You may want to change the while loop into a for loop with smaller iterations so you can control how many records are merged in each go

while (true){
Zot_Dup_Pane.merge()


}

Speaking as a non-coding geek, do any of these scripts work for macintosh?

I should have clarified that I used my mac to both create and test the Sikuli script. I had to restart it a few times to merge all of the duplicates, because it would hang up for some reason - maybe because it didn't recognize all of the non-article icons.

@rachelmurray25 that was very helpful! I can make it work but I have issues when I have duplicates of different nature (i.e., six conference papers and one journal) which are recognized as duplicates but it won't let me merge them unless they have the same nature. Could you manage to automate that process too?

I found a way to (kind of) automate it, which works for me so far.

Open up the Duplicate Items folder. Go to Tools > Developer > Run JavaScript

and use this Snippet:

var DupPane = Zotero.getZoteroPanes();
for(var i = 0; i < 100; i++) {
await new Promise(r => setTimeout(r, 1000));
DupPane[0].mergeSelectedItems();
Zotero_Duplicates_Pane.merge();
}

Basically, this click 100 times the "Merge X items" button with a second waiting time in between. This worked well for me, as I had to merge some thousands of items after importing multiple files. Maybe that helps someone. As I am not really aware of any implications / side-effect this function may have, use it with caution!

In the desktop version you have the Tools > Developer > Run Javascript menus.

Perhaps I am mistaken, but I think the reason that you get `TypeError: oldestItem is undefined` is that you have not selected any of the entries (i.e., you clicked on the Duplicate Items *collection* but did not click on any of the items that appeared within the resulting view). "Fixing dates" only appears to solve the problem because in the process of doing that you incidentally selected an entry.

I imported references on several occassions, each with its own collection.

Well, what do you mean by that? If you use Zotero's official Mendeley importer multiple times, it won't create duplicates. If you imported from a file multiple times, those would have distinct Date Added values.

@aurimas re comment of September 17, 2014; I cannot seem to add multiples items from the 'Duplicate items' special collection to a tag in the lower left panel.

@marcelparciak
Your trick seems to be working for me. Running it now. No problems so far.

The applet "autoclicker.exe" is another useful resource in this situation, at least for Windows 10. (It does exactly what the name implies.)

@a.abdul-rahman

You can use Zutilo to copy a tag to all selected items.

Thank you @marcelparciak for your script.

It works for a few items, then I get the message: TypeError: oldestItem is undefined

Any idea why?