Zotero Connector plugin blocks IP on ScienceDirect (unable to download PDFs)

lucywheeler
The Zotero Connector plugin (Version 5.0.210) causes a block on my IP address when trying to access PDFs on ScienceDirect. After contacting Elsevier I was told that this was due to their system detecting "activities matching the patterns associated with automated activity". I cannot either download PDFs automatically to my Zotero library using the Connector plugin (the plugin saves the reference, but only a snapshot) or manually view/download PDFs unless the plugin is disabled. I believe this must be due to ScienceDirect/Elsevier enacting stricter anti-bot measures, is there anything that can be done to at least make it possible to manually download PDFs while the Zotero Connector plugin is enabled?

Error message from Zotero Connector plugin:
Info: Service worker starts: 2026-07-21 15:39:47
[JavaScript Error: "Method saveAttachmentFromResolver failed
Connector Communication Error: Method saveAttachmentFromResolver failed
at chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/messaging_inject.js:85:17
at async ItemSaver.saveAttachmentFromResolver (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/itemSaver.js:338:16)
at async ItemSaver._saveAttachmentsToZotero (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/itemSaver.js:316:5)
at async Promise.all (index 0)
at async ItemSaver.saveAttachmentsToZotero (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/itemSaver.js:252:3)
at async ItemSaver._saveToZotero (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/itemSaver.js:213:5)
at async ItemSaver.saveItems (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/itemSaver.js:96:11)
at async Object.onTranslate (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/inject/pageSaving.js:597:16)
at async messageListener (chrome-extension://nmhdhpibnnopknkmonacoephklnflpho/messaging_inject.js:128:15)" {file: "[object Object]"}]

Error message from ScienceDirect on attempting to access a PDF:
There was a problem providing the content you requested
Please contact our support team for more information and provide the details below.

Reference number: a1eae3a8af00955d
IP Address: xxx.xx.xx.xxxx
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/150.0.0.0 Safari/537.36 Edg/150.0.0.0
Timestamp: 2026-07-21 14:27:57 UTC
CPE00001
  • dstillman Zotero Team
    edited 13 days ago
    The Zotero Connector simply being enabled or disabled wouldn't have any effect on this — the Connector only operates when you try to save things. But if you try to download many items at once with the Connector, particularly with PDF-saving enabled, ScienceDirect could certainly block you, since you're essentially making bulk automated requests.

    At this point, your IP address would be blocked, so you'll likely need to wait a bit before you're allowed again. Disabling the Connector wouldn't help with that.
  • lucywheeler
    Thanks dstillman, however I am only trying to download single items. I also can't view a single PDF (by clicking "View PDF" on the ScienceDirect article page). I cannot download or view any PDFs while the Zotero plugin is enabled, as my IP address gets blocked by ScienceDirect.
  • dstillman Zotero Team
    edited 13 days ago
    Again, this wouldn't have anything to do with the Zotero Connector being enabled. You can test this yourself by disabling the Connector — there shouldn't be any difference in your access. Your IP address is already blocked from previous activity (either by Zotero or something else — there's no way to know for sure). All you can do now is wait or switch to a different network.

    ScienceDirect uses strict anti-bot measures, but we haven't had any other reports of single-file saves causing ScienceDirect to block people, so a previous multi-item save would be the most likely cause.
  • lucywheeler
    Thank you for this advice. I am currently still blocked but was able to access ScienceDirect PDFs earlier today after clearing all cookies and disabling the Connector plugin, and was only blocked again after re-enabling the plugin (immediately after attempting to save one paper, I did not make any bulk requests). This is also an issue other members of my organisation are facing, so it may have something to do with our network/security system. However it does seem to be triggered by using the Connector plugin.

    I have already contacted Elsevier and was told to disable all plugins, so would you just recommend that I don't use the Connector plugin?
  • dstillman Zotero Team
    edited 13 days ago
    Once again, there's absolutely no reason to disable the Connector. Having it enabled has no effect on whether you can access PDFs on ScienceDirect. You should leave it enabled if you're using Zotero.

    If you're getting blocked by ScienceDirect after single-item saves using the Connector, that's another matter, and we can look into that. This is the first report we've gotten of that.
  • lucywheeler
    Thank you. I am still blocked so can't replicate the block I received earlier today after re-enabling the plugin, but I have asked the other people who are having similar access issues with ScienceDirect and see what effect using the plugin has on whether they get blocked and let you know if it seems to be specifically related to the plugin. Thanks again for your help.
  • dstillman Zotero Team
    edited 13 days ago
    Note that if your organization has a single outgoing IP address, activity from one person (again, from Zotero or anything else) could trigger a block for everyone.

    But if other people aren't currently affected, and you think saving from the Connector triggers this, we'd want to see a Debug ID from the Connector for reloading a ScienceDirect page, trying to save, and ending up blocked. A Debug ID wouldn't be useful after someone was already blocked, so this is only helpful if you really think you can reproduce it by saving.
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