How to Set Up Zotero Sync Without Paying for Storage
Direct answer: Zotero syncs metadata for free but charges for PDFs. Point attachment sync at a WebDAV host (Koofr, Box, or a self-hosted Nextcloud) and the 300 MB cap stops applying entirely.
This is the single most useful thing to know about Zotero that the welcome screen doesn’t tell you. Data sync and file sync are separate settings. Your library of 4,000 citations costs nothing forever. It’s only the PDFs that hit a paywall.
Why does Zotero charge for storage at all?
Because hosting PDFs is genuinely expensive and the project is nonprofit-funded. The free tier is 300 MB; the paid tiers are $20/year for 2 GB and $60/year for 6 GB, with unlimited at $120.
For an undergrad writing one thesis, 300 MB might be enough — that’s roughly 60-80 journal PDFs. For a PhD student or a research group, it’s a wall you hit in the first month. WebDAV exists precisely for this case, and the Zotero developers document it rather than hide it.
How do you split data sync from file sync?
Two tabs, one critical checkbox.
- Open Settings → Sync.
- Enter your zotero.org credentials. Leave Sync automatically on.
- Untick “Sync attachment files in My Library using Zotero storage”. This is the switch that keeps PDFs off Zotero’s servers.
- Click Verify Server before you enter anything else. If the URL is wrong, sync fails silently for hours.
After this, metadata flows through zotero.org and annotation highlights sync too, while the PDF binaries go wherever your WebDAV points.
Which WebDAV provider should you use?
| Provider | Free space | Works well? | Catch |
|---|---|---|---|
| Koofr | 10 GB | Yes, most common choice | App password required, not your login |
| Box.com | 10 GB | Yes | Needs a paid-tier feature for WebDAV on some accounts |
| Nextcloud self-hosted | Your disk | Yes | You handle backups |
| Google Drive | — | No | No native WebDAV endpoint |
| Dropbox | — | No | Dropped WebDAV support |
Koofr is what most people end up on: 10 GB free, real WebDAV endpoint, and a separate app password you can revoke. Get the app password from Koofr → Preferences → Password, not your account password — Zotero will reject the latter.
What are the exact settings for Koofr?
- URL:
https://app.koofr.net/dav/Koofr - Username: your Koofr email
- Password: the app-specific password, usually 8-10 characters
Click Verify Server. A green check means it’s reachable. Then click Sync Now and watch the progress. Zotero creates its own zotero folder at the root — don’t point it at a subfolder you’ve already filled with other files.
What breaks with WebDAV sync?
Four things, and you’ll hit at least one.
Deletion doesn’t propagate cleanly. Deleting an item’s attachment in one machine can leave orphans in the WebDAV store. They don’t count against Zotero’s quota, but they do consume your Koofr space, and nothing warns you.
Shared group libraries need Zotero storage. WebDAV file sync is for My Library only. If you collaborate in a group library with shared PDFs, that traffic goes through Zotero and hits the paid tier. This is the most common gotcha in lab settings.
iOS and mobile are inconsistent. Zotero’s mobile app expects Zotero storage for on-demand downloads. With WebDAV, PDFs may fail to open on mobile even though metadata syncs fine.
Rate limits on free hosts. Koofr and Box throttle bulk uploads. If you’re syncing 3,000 PDFs for the first time, do it overnight. A 4,000-file upload can take hours and will look stalled.
Is WebDAV the right choice for you?
Yes, if you’re one person with a large personal library and no shared PDFs. That describes most grad students and almost all independent researchers.
No, if you work in a group library or need reliable mobile reading. In those cases $20/year for 2 GB is the honest answer, and fighting WebDAV will cost you more in lost afternoons than the subscription costs in money.
What about managing annotations across devices?
Highlight and note sync happens through data sync, not file sync — good news, since that’s the free half. Read and annotate on a laptop, and the highlights show up on any other machine within a few minutes of Zotero being open. The underlying PDF must exist on both machines though, which is where the WebDAV attachment arrives.
If a device shows annotations but no PDF text, the attachment sync is lagging. Force it with Sync → Sync Now rather than deleting and re-adding the item, which loses your annotations.
Key Takeaways
- Zotero’s free 300 MB cap applies only to attachment files, not metadata.
- Untick “Sync attachment files using Zotero storage” to route PDFs to WebDAV.
- Koofr gives 10 GB free with a real WebDAV endpoint; use an app password.
- Group libraries always need paid Zotero storage — WebDAV won’t work there.
- Bulk first sync takes hours; run it overnight.
