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A Zotero library of 3,000 papers is mostly PDFs in one folder you can move

Zotero stores every attached PDF in its storage folder. How big it gets, how to find the biggest attachments, and how to move or trim it safely.

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Zotero keeps its database and every attached file in one data directory, by default ~/Zotero. The database is small. The storage folder, with a subfolder per attachment, holds every PDF, and for a long research career that is many GB.

du -sh ~/Zotero ~/Zotero/storage
du -sh ~/Zotero/storage/* 2>/dev/null | sort -h | tail -10

Each subfolder has a random eight character name. Open the biggest in Finder to see which paper it is.

Find very large attachments

find ~/Zotero/storage -type f -size +50M -exec du -h {} + 2>/dev/null | sort -h

Usually these are scanned books, theses and supplementary data. In Zotero, delete an attachment you do not need by selecting it and pressing Delete; that removes the file too.

Moving the data directory

  1. Quit Zotero.
  2. Move the whole ~/Zotero folder to its new location, for example an external drive.
  3. Open Zotero, go to Settings, Advanced, Files and Folders, and set Data Directory Location to the new place.
  4. Restart Zotero.

Linked files

Zotero can link to PDFs kept elsewhere instead of storing them in its folder. That does not save space by itself, but it lets you keep papers in a folder you manage.

Other academic tools: MacTeX and Mac storage for academics.

Related: Anki media taking up space on Mac.

Common questions

Where does Zotero store PDFs on a Mac?

In the storage folder inside the Zotero data directory, by default ~/Zotero/storage, with one subfolder per attachment.

How do I move my Zotero library to another drive?

Quit Zotero, move the whole Zotero folder, then set Data Directory Location in Settings, Advanced, Files and Folders, and restart.

Can I keep Zotero in iCloud or Dropbox?

Not the data directory. Syncing the database while Zotero is running can damage it. Use Zotero's own sync instead.

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