The information from Zotero help (last modified on July 2025)
The Zotero Connector for Safari requires macOS 11 Big Sur or later.
The Zotero Connector for Safari is bundled with the Zotero desktop app. (Current versions of Safari don't allow direct installation of browser extensions like other browsers.) After opening Zotero for the first time, you can enable the Zotero Connector from the Extensions pane of the Safari settings (“Safari” menu → “Settings” → “Extensions”, not “Safari” menu → “Safari Extensions…”)
If you find that the extension isn't listed in the Safari settings or the toolbar button isn't appearing or working properly, follow these steps:
Delete the Zotero app from Applications
Redownload it from the download page
Start Zotero
Alternatively, to avoid redownloading the app:
Compress the Zotero app in Applications (right-click → “Compress “Zotero””)
Delete the app
Double-click the ZIP file
Delete Zotero.zip
Start Zotero
In either case, your Zotero data won't be affected.
It may also help to restart your computer in between deleting the app and restoring it, though this isn't usually necessary.
Currently, the only known way to avoid this is to switch to a browser with a more reliable extension framework such as Firefox, Chrome, or Edge.