I was able to come across a solution for this. In my safari browser I was seeing the error message. Failed to load resource: You do not have permission to access the requested resource. The problem was in the changes I made in an attempt to fix errors I was seeing in the Safari settings under my extension (errors such as - "Failed to load images in default_icon for the browser_action or page_action manifest entry.", "Failed to load images in icons manifest entry.", "The service_worker script failed to load due to an error"). So I changed some paths in my manifest.json and got ride of those errors. Without realizing, those changes screwed up the way I was trying to load my web_accessible_resources via chrome.runtime.getURL. Here is my web_accessible_resources section in my manifest.json. . . "web_accessible_resources": [ { "resources": ["dist/panel.html", "dist/iframeListener.bundle.js"], "matches": ["<all_urls>"] } ] . . Here's how I was calling it in my logic private initPanel(): HTMLIFrameElement { . . . // wrong iframeReference.src = chrome.runtime.getURL("panel.html"); . . . } Here's how I fixed it private initPanel(): HTMLIFrameElement { . . . iframeReference.src = chrome.runtime.getURL("dist/panel.html"); . . . } These changes are great but temporary - ideally I shouldn't need to change paths in my manifest.json to get this working for safari. As part of my build process I generate a "dist" directory which includes a copy of my manifest.json this is the manfest.json that Xcode should be picking up thereby allowing chrome.runtime.getURL("panel.html"); to work. But Xcode picks up the wrong manifest.json (the one in my projects root folder) so I am manually prepending "dist/" to my paths in this manifest. I think I need to modify some setting in Xcode so that it picks up the right manifest. I am just not familiar with Xcode so I'm working through it.

I'm facing the same issue after migrating my chrome extension to safari. Were you able to make progress on this?