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:
    The "Prevent Duplicates" add-on that he mentions (which does what you want but for Firefox only) is here:
    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 15 days ago
    Is it maybe possible for Zotero to automatically warn about it after adding a potential duplicate?
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