Check if references is already in library before saving it?

Hello, I wonder if it's possible to check from firefox if the reference is already in the library without saving it and then checking duplicates. It should be an easy operation but I don't see any option to do that. Do I really have to add it and then check if it's a duplicate? It sounds silly.
  • There is currently no way to check whether an item is already present in the library before saving. My recommendation is to not worry about it--just save items and periodically use the Merge Duplicates feature to clean up your library in batches.

    (There is a plugin that enables such a pre-flight check when trying to save items, but it is not maintained by its author and will stop working when Zotero 5 releases later this year.)

    This is actually a very challenging technical problem. Complete support for pre-saving duplicate checking would require Zotero to essentially run its save function on every item on every page you load in your browser. This would have a terrible impact on performance and speed. Support for a more limited check that should cover most cases without seriously impacting performance (checking for identical DOI or URL) is planned, but no estimate for when it will arrive.
  • edited November 18, 2016
    Thanks for the reply. Are you saying it's not easy to implement the following working scheme?
    1 User clicks save button
    2 Zotero checks if title/authors/etc combination is in library without saving.
    if not present save
    else prompt user for cancel save operation or continue.

    The function that reads the tile/author from the webpage extracts only that information and uses it with a lookup function to check if duplicate exists in library. Why do you have to save all information before being able to do that?
  • The way Zotero saves items, the concept of "just" looking up author/title doesn't make sense (e.g. because Zotero downloads a citation data file in RIS format or so to import anything at all), so it's all or nothing.
    The relevant ticket for the DOI/URL check bwiernik describes is here: https://github.com/zotero/zotero/issues/1007
    The "Prevent Duplicates" add-on that he mentions (which does what you want but for Firefox only) is here: https://github.com/adam3smith/zotero-prevent-duplicates/
    Contributions to both welcome.
  • edited August 11, 2021
    F1000/Sciwheel does this just fine. I am really disappointed Zotero cannot. It causes a big problem for me.

    If I highlight or comment on a PDf and merge the wrong one (how am I supposed to know which version I commented on 2 years ago???), I could lose my notes, often very important notes. I already lost some in the middle of writing a grant.

    It also takes time and has issues if the files are not the same format. With F1000/Sciwheel, I could save to references and it if was already saved it would ignore my new save and the PDF I uploaded before would be the only version. this is also the case if there is no PDF. I wonder why this is not the case for Zotero? Do all other reference managers besides F1000 do this or only Zotero???
  • (Zotero doesn't delete PDFs when you merge duplicates -- they're both available under the merged item)
  • Okay, but then I have to open all the duplicates to find the one with my highlights/comments. If I am lucky they are all on one PDF? Wouldn't it be better if it just didn't create the duplicate in the first place?
  • Absolultely would be better. I don't think anyone disagrees this is a highly desirable feature.
  • Yes, it would. Again, everybody agrees with you. It is probably one of the many highly desirable features the developers would like to implement when they can get to it.
  • edited August 30, 2021
    Merge isn't a great solution because I don't really care if I have 2 references - I care that I don't know which PDF I've annotated....
  • edited October 5, 2021
    Is it maybe possible for Zotero to automatically warn about it after adding a potential duplicate?
  • Warning before adding it would be nice but if not warning after adding it would also prevent problems like the duplicate annotation of papers.
    Just wanted to show my support for this feature (and bump it up)
  • Completely agree. All we need is a prompt that the paper is already in Library right after it has been added.
  • edited May 21, 2024
    For me this is the main reason I'm using Readcube/Papers, since it's the only service with a browser plugin which provides a direct indication when something is already in my library. Would love something like this for Zotero.
  • edited May 21, 2024
    The Zoplicate plugin flags a duplicate as it is being added to Zotero, giving you the option to keep just the original version, the new one, or both.
    https://chenglongma.com/zoplicate/
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