Upgrade StorageGroup Library PDFs Open as Black Screen (Web + Desktop), Only One File Opens Normally
Hello everyone,
We are facing a serious issue with a Zotero group library and would really appreciate some guidance.
Problem description:
Almost all PDFs in our group library open as a completely black screen.
This happens both in:
Zotero Desktop, and
Zotero Web.
However, one PDF in the group opens correctly everywhere, and all PDFs in personal libraries open normally.
This problem affects multiple users in the same group.
https://s3.amazonaws.com/zotero.org/images/forums/u14731110/4fnfitab4b0ncf8gjf1g.png
On the Zotero website, one file opens correctly, but almost all other group PDFs still show a black screen. This strongly suggests a server-side corruption of the group attachment metadata, not a local client issue.
At the moment, this problem is blocking access to our shared research materials for the entire group.
Has anyone experienced something similar, or is there a way for Zotero staff to repair the corrupted group attachments on the server?
Thank you very much for your help.
We are facing a serious issue with a Zotero group library and would really appreciate some guidance.
Problem description:
Almost all PDFs in our group library open as a completely black screen.
This happens both in:
Zotero Desktop, and
Zotero Web.
However, one PDF in the group opens correctly everywhere, and all PDFs in personal libraries open normally.
This problem affects multiple users in the same group.
https://s3.amazonaws.com/zotero.org/images/forums/u14731110/4fnfitab4b0ncf8gjf1g.png
On the Zotero website, one file opens correctly, but almost all other group PDFs still show a black screen. This strongly suggests a server-side corruption of the group attachment metadata, not a local client issue.
At the moment, this problem is blocking access to our shared research materials for the entire group.
Has anyone experienced something similar, or is there a way for Zotero staff to repair the corrupted group attachments on the server?
Thank you very much for your help.
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
Thank you very much for investigating this issue and for the detailed explanation.
From our side, we would like to clarify the current situation and ask for guidance on how to proceed without losing existing data.
At the moment, three group members are affected by this issue and are unable to open many files in the group library:
sreeram.ramakrishnan@mailbox.tu-dresden.de
martin.baumgarten@tu-dresden.de - Debug Id: D243653756
johannes.koal@tu-dresden.de
However, one group member (tony.richter1@tu-dresden.de - Debug Id: D1157004639) is able to access and open all files in the group library normally, without seeing the black screen or empty-file behavior.
This group library contains very old material, including contributions from former students, and—most importantly—a large number of notes, highlights, and annotations that we need to retain. Because of this, we are very concerned about taking any action that might overwrite or delete existing notes or markings stored on the Zotero servers.
Could you please advise us on:
The safest way to resolve or repair the empty (zero-byte) files in the group library
Whether it is possible to restore or reattach the correct PDFs without affecting existing notes and annotations
Whether one unaffected group member (who can still access all files) could be used as a reference source for recovery
Preserving the historical notes and annotations is extremely important for our ongoing research, so we would appreciate guidance on the best workflow to handle this safely.
Thank you again for your time and support.
Kind regards,
Sreeram Ramakrishnan
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
See my previous message for what you should check on your own computer.
Notes and annotations are stored in the Zotero database and wouldn't be affected. Replacing the file with a copy that was identical to the original would allow you reopen the file with the annotations in the same place.
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
I previously shared a Debug ID generated from my supervisor’s system. However, we would like to clarify that the file corresponding to that Debug ID is no longer available locally with us, as it was uploaded to Zotero a long time ago and we do not have an external copy anymore.
Since this file was previously available in the Zotero cloud, we would greatly appreciate your help in checking whether it is possible to retrieve or restore it from the server side.
For reference, the Debug ID is:
D362766890
Thank you very much for your support.
Regards,
Sreeram Ramakrishnan.
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.
I have now checked locally on my system for the file keys you shared earlier, and on my side the corresponding files are not available locally anymore. These attachments were added a long time ago, and I no longer have separate external copies of them.
My supervisor is currently checking the same file keys on their system and will revert shortly with their findings.
In the meantime, since this situation is affecting a long-standing group library with important research data, I wanted to ask whether there is any possibility of discussing this issue directly with support (e.g., via a call or gmeet) , if that would help move things forward more efficiently. We completely understand if email/forum is the only supported channel, but wanted to ask given the complexity of the case.
Thank you for your continued time and support. We will follow up again as soon as my supervisor completes their local checks.
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.
All the zero-byte files you added, which I listed, also haven't changed since a single day in November 2024. The other files you've added are still fine. I'm not sure you're not engaging with what I'm saying about the number of files affected. Again, 1/3 of your files are empty. The other 2/3 are not. You can open the other 2/3 of files on the web library, and unless they're corrupted in some other way, they should work. If someone can't open a file locally that's available in the web library, that's more evidence that security software on your systems is blanking out files. No, we don't have user-level backups, and we make no claim to that effect. Synced Zotero data and files can be used to restore a library in the event of a computer crash, etc., but only the latest library state is available. In this case, something on your systems appears to have overwritten the files with empty files, which Zotero then uploaded, since Zotero automatically uploads all locally modified files.
We only provide support via these forums, sorry. But there's not really anything else we can say here other than that something on your systems — seemingly going back over a year — has been emptying out local files, which Zotero then uploaded. We haven't received other reports of this and have no reason to think this is a bug in Zotero itself.
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
Looking at the timestamps here, though, it looks like this issue is no longer occurring. All the zero-byte files were updated between November 7, 2024 and August 4, 2025. (The attachments were added at different times, but that's when they were updated to be zero bytes.) The 2/3 of files updated before or since are unaffected. The affected files were updated by different people in the group. So something was likely happening on your systems between those dates that affected all your systems.
Those files will need be replaced. You can download them again using your browser and replace the files directly in their respective 'storage' folders, replacing the zero-bytes files. Zotero will then re-upload them. As long as you replace them with the identical files, Zotero-created annotations will be in the same position.