Can you provide a Debug ID for trying to open a PDF?

[JavaScript Error: "InvalidPDFException: Worker 'import' failed: {"existingAnnotations":[],"error":"{\"message\":\"The PDF file is empty, i.e. its size is zero bytes.\",\"name\":\"InvalidPDFException\"}"}" {file: "chrome://zotero/content/xpcom/pdfWorker/manager.js" line: 324}]

You have lots of empty (zero-byte) files in the library, all uploaded around November 3–4, 2025. Files added before then and after then are mostly fine (except for a few files added in June 2025), so it's not all files. About 1/3 of the files in the library are empty.

I don't think we've ever seen anything like this, and the files in question seem to have been added by various people in the group, so I would guess this is due to shared security software on your computers. This is also affecting webpage snapshots, which are zipped before they're uploaded, and in your case are valid zips of empty .html files, so it would have to have been something happening locally, not a server-side problem.

Individual members can right-click → Show File on a file they added, on the computer where they added it, to see if their local copy is zero bytes. E.g., you can paste some of these into the search bar in All Fields & Tags mode to see some of the files that you added that are empty online:

9J5MQSL5
G97IXLS5
NHC87N22
SRWIRH96
VNLRHMV3
Z48ALL74

Hello Mr. Dstillman,

I would like to provide a correction and an update to my previous message.

Earlier, I mentioned that one group member (tony.richter1@tu-dresden.de) was able to open all files in the group library. However, after updating Zotero to the latest version and performing a full resynchronization, he is now also unable to open the affected PDFs and sees the same black screen / empty-file behavior as the rest of us.

This means that all tested group members are now affected, and no one can currently open the majority of the PDFs in the group library.

We have also generated a Debug ID from attempting to open one of the affected group PDFs on his system after the update and resync:

Debug ID: D451320095

We wanted to clarify this as soon as possible, since it may be relevant for diagnosing whether the issue is related to how newer Zotero versions handle these zero-byte attachments.

Please let us know how best to proceed, especially with regard to safely restoring the files while preserving the existing notes and annotations, which are very important for our ongoing research.

Thank you again for your continued help.

Kind regards,
Sreeram Ramakrishnan

I would guess that security software (or malware) on one or all of your computers is causing the files to become empty, and Zotero is then dutifully propagating those modified, empty files to other members' computers. But you'd need to check what I say for us to say more.

Hello Mr.Dstillman,

I wanted to share a brief response from my supervisor regarding this issue:

“Can you please write to Zotero support again? Nearly all of my attachments are gone, including some that I am sure were available in the cloud earlier. I think this might be something that could be refactored or repaired on the server side.”

My Supervisor zotero mail: johannes.koal@tu-dresden.de

We wanted to pass this along for your awareness, as the potential loss of cloud-stored attachments is a major concern for our group.

Thank you for your continued support.

Regards,
Sreeram Ramakrishnan

You have access to the same files that we do. Something on your systems has modified 1/3 of the group files locally to be zero bytes, which Zotero then correctly uploaded. The other 2/3 of files are non-empty, so it's simply not the case that "Nearly all of [the] attachments are gone".

I provided a list of files above for you personally to check locally. You have yet to respond to that, and we can't help you further until you do.

Hello Mr. Dstillman,

As a follow-up, my supervisor has now checked all of the file IDs you mentioned.

He is also unable to open any of those files, because they are not available locally on his system. He originally uploaded all of these files directly to Zotero and does not have separate local backups of them anymore. At the time, Zotero cloud storage was used as the primary and trusted location for these attachments.

For the account johannes.koal@tu-dresden.de, the situation is even more severe: no files are opening at all, and almost all attachments appear as 0-byte files.

Given that these files were uploaded to Zotero and stored in the cloud, my supervisor would like to ask whether any backups exist on your side that could be used for recovery. From his perspective, this is precisely the reason for relying on Zotero’s cloud service.

Because this issue affects a large, long-standing research library and we no longer have local copies to recover from, we kindly ask whether it would be possible to have a short call or online meeting with support to discuss the situation and possible recovery options in more detail.

Thank you for your continued attention to this matter. We would greatly appreciate any guidance on how best to proceed.

Hello Mr Dstillman,

Thank you for the detailed explanation. We would like to clarify our understanding and confirm next steps, based on what you’ve described.

We have now done exactly what you suggested: for the listed items, we used Right-click → Show File in Zotero on multiple affected systems. For many of these files, the local copies are indeed 0 bytes, which matches what we see both locally and in the web library. So to confirm, even after following all these steps, the files remain zero bytes on our systems.

From your explanation, we want to confirm our understanding:

There are no server-side or historical backups available for user attachments beyond the current state.

Since Zotero syncs the current local file state, once a file becomes zero bytes locally and is uploaded, the original content cannot be recovered from the server.

Therefore, the only way forward for the affected files is to re-upload the original PDFs, if they can be found from any external source.

Could you please confirm if this understanding is correct?

We also wanted to clarify the statement about “1/3 of the files”. Our understanding is that this refers to approximately one-third of the total attachments in the library being affected, not that each file was uploaded three times. However, we have noticed cases where multiple attachments belonging to the same item appear as zero-byte files, and we wanted to confirm whether that aligns with what you are seeing on your side.

One additional point that is confusing for us: one of our colleagues was able to open some of these files successfully about three weeks ago. After updating Zotero and performing a full resync, he is now also unable to open those same files, and they appear as zero bytes. This makes it difficult for us to understand when and how the files were actually overwritten.

Finally, we would really appreciate it if you could elaborate a bit more on the likely root cause you mentioned (e.g., security software or system-level processes). If we better understand what kind of software or behavior could cause local files to be silently overwritten with empty files, we can work with our IT department to ensure this does not happen again in the future.

Thank you for your patience and for continuing to engage with us on this issue. We understand the limitations you’ve explained and mainly want to be sure we fully understand what happened and how to prevent a recurrence.

Kind regards,
Sreeram Ramakrishnan