Safari Extension Error: “Non-persistent background content cannot listen to webRequest events.” after macOS 15.4 / Safari 18.4 Update
We’re seeing the following error in the Safari Extensions tab after updating to macOS 15.4 and Safari 18.4:
“Non-persistent background content cannot listen to webRequest events.”
This error did not appear prior to the update, and we haven’t found any official documentation stating that webRequest API is no longer supported in Safari.
In our extension (Manifest V3), we are using the webRequest.onHeadersReceived callback to intercept response headers and read updated cookies. While the functionality itself still works as expected. we’re able to access the response headers and this error is now shown in the Extension settings page.
We are not seeing this issue in other browsers (Chrome, Firefox) using the same Manifest V3 setup.
Is there any plan to deprecate webRequest support in Manifest V3 for Safari?
We’d appreciate any clarification or guidance on how to handle this going forward.