Zotero Storage Plans and Quota Management

Zotero’s own library — item metadata, notes, tags, and collections — syncs free and unlimited through Zotero’s servers no matter how large it grows. The thing that actually runs into a wall is attached files: PDFs, snapshots, and other documents draw against a separate, metered storage quota, and the free tier is a modest 300 MB. Most people who hit the limit assume their whole library is too big; almost always it’s a handful of large PDFs, and the fix is a choice about attachments, not a purge of references.

What actually uses your storage quota

Zotero’s sync has two independent layers, and only one of them is metered:

Bibliographic data — item metadata, notes, tags, collections, and saved searches — syncs free and unlimited through Zotero’s own servers, regardless of library size.
File attachments — PDFs, images, snapshots, and other documents you’ve stored inside Zotero — count against your storage quota, and only these do.

That distinction matters because it means quota pressure is entirely a function of how many stored file copies you’re carrying, not how many references you’ve saved. A library with 5,000 items and no attached PDFs uses close to zero storage; a library with 200 items and full-text PDFs stored on every one can fill 300 MB quickly.

Zotero’s storage plans and pricing

Zotero (zotero.org/storage) sells storage in four tiers:

Free — 300 MB
2 GB — $20/year
6 GB — $60/year
Unlimited — $120/year

Zotero also sells separate, quote-based storage plans aimed at labs and institutions, for teams whose attachment volume outgrows the individual tiers. The free 300 MB allowance isn’t a time-limited trial — it’s a permanent tier, and plenty of Zotero users with metadata-heavy, attachment-light libraries never need to pay for storage at all.

You can see your current usage against your plan from your account settings at zotero.org — worth checking before assuming you need to upgrade; it’s common to be much closer to (or further from) the limit than expected once you account for how much of it is a handful of oversized attachments.

Stored vs. linked attachments — the single biggest lever

The detail that actually controls quota consumption is a choice Zotero makes you at the moment you attach a file, and it’s easy to miss because the default just works:

Stored copy of file (the default) — Zotero copies the file into its own data directory, syncs it across your devices through Zotero’s servers, and counts it against your storage quota. Deleting the attachment item frees that quota back up.
Linked file — Zotero stores only a reference to the file’s location on disk (or on a drive/cloud folder you manage yourself), never counts it against your quota, and never syncs it through Zotero’s servers. The tradeoff is that a linked file doesn’t follow you to another device automatically — you need your own file-sync tool (an institutional file share, a cloud-storage folder) for that — and linked attachments aren’t supported in group libraries or Zotero’s mobile apps.

You choose which one you get: the paperclip “Add Attachment” menu on a selected item offers “Attach Stored Copy of File…” and “Attach Link to File…” separately, and the same choice exists under “New Item” as “Store Copy of File…” and “Link to File…”. Dragging a file directly into Zotero creates a stored copy by default — hold Ctrl+Shift (Windows/Linux) or Cmd+Option (Mac) while dragging to create a link instead.

In practice this makes linking the right call for large PDFs you already keep organized somewhere durable — an institutional file server, a departmental shared drive, a personal cloud-storage folder you sync independently — and storing the right call for anything you want to travel automatically with your library across devices, especially anything you’ll open on a phone or tablet via Zotero’s apps.

Self-hosting file storage with WebDAV

Beyond linking individual files, Zotero supports replacing its own hosted file storage entirely with a WebDAV server — a standard protocol for transferring files over the web. This is a genuine third path, distinct from both Zotero’s paid tiers and manually linking files one at a time: attachments still sync automatically across your devices, but through your own WebDAV space instead of Zotero’s metered storage.

Setup happens in Zotero’s Sync preferences, under file syncing: you supply the WebDAV server’s URL, your username, and your password, choose http or https (try https first if you’re not sure which your provider uses), then use “Verify Server” to confirm the connection before relying on it. Two limits to know before switching:

Personal libraries only. Group libraries cannot use WebDAV — a group’s attachments always sync through Zotero’s own storage, drawing on the group owner’s plan.
No Zotero support for the server itself. Zotero’s own documentation is explicit that its developers can’t troubleshoot a third-party WebDAV server — if your institution runs one, that’s a question for your IT department, not Zotero support.

WebDAV is the natural fit for researchers at an institution that already runs (or licenses) WebDAV-accessible storage — it sidesteps Zotero’s paid tiers entirely rather than trading one library’s convenience for another’s, at the cost of depending on a server Zotero itself has no visibility into.

Practical tactics for staying under quota

Link large PDFs you already store elsewhere rather than letting Zotero make a second copy — the single highest-leverage change for anyone with a big attachment backlog.
Be selective about what you store, not just how much. A paper you cite once from memory of its abstract doesn’t need a stored full-text copy the way one you’re actively annotating does.
Delete superseded stored attachments — a replaced PDF (a corrected proof, a newer preprint version) left attached to the old item is pure waste; deleting a stored attachment reclaims its quota immediately, where deleting a linked one never affected quota to begin with.
Move to WebDAV if you have institutional storage available rather than repeatedly paying Zotero’s per-GB tiers, especially for a library with a genuinely large, growing attachment volume.
Mix strategies deliberately — store attachments for the smaller set of papers you read on multiple devices or annotate heavily, link everything else. Zotero supports both in the same library, item by item.

Group libraries: quota belongs to the owner, not the group

Group storage doesn’t pool across members — it draws entirely on whichever individual’s account owns the group. Five collaborators each attaching PDFs to a shared group can exhaust the owner’s 300 MB free tier fast, even though none of them has a large personal library of their own. If you’re setting up or managing a group’s storage specifically — choosing a paid tier sized to the group’s real attachment volume, or transferring ownership so the group doesn’t depend on one researcher’s account — see the full group-library setup guide for the permission model and ownership mechanics; this page focuses on managing quota, not on group setup itself.

What happens when you hit the limit

Once a storage account is full, new file attachments stop syncing to Zotero’s servers until you upgrade the plan, free up space, switch some attachments to linked files, or move file syncing to WebDAV. Bibliographic syncing — the metadata layer — keeps working regardless, since it isn’t metered at all; you won’t lose access to your references, only to adding further stored files until you address the quota.

Frequently asked questions

Does the 300 MB free tier expire?
No — it’s a permanent allowance, not a time-limited trial. Many libraries with light attachment use never need to upgrade.

If I delete a linked attachment, does that free up quota?
No — linked files were never counted against your quota, so removing one doesn’t change your usage. Only deleting a stored attachment reclaims space.

Can I switch an existing stored attachment to a linked one later?
Yes, in general — you can remove the stored copy and re-attach the same file as a link instead. There’s no automatic bulk-convert switch for an entire library; it’s a per-item change.

Does using WebDAV make Zotero cheaper?
It replaces Zotero’s own paid tiers with your own WebDAV-accessible storage, so the actual cost depends entirely on what that storage costs you — free if your institution already provides it, priced separately if you’re paying a third-party WebDAV provider. Zotero itself doesn’t charge anything extra once you’re syncing through WebDAV.

Do collaborators need their own paid Zotero plan to join a group?
No — joining a group and adding or editing items doesn’t require a paid plan. Only the group’s file storage draws against a paid tier, and that’s the owner’s plan, not each member’s.