There are multiple ways to embed a webview in an app. The SFSafariViewController is an out of process webview that you can embed in your app. It can share cookies with Safari and it will use whatever content blocker you have installed. The hosting app doesn't have any access to the cookies or any information you type in. Feedly uses this web view. https://stackoverflow.com/questions/32681511/deactive-ios-9-...

Firefox doesn't use SFSafariViewController. It uses the WKWebView (?). The WKWebView gives the hosting app a lot more control over the webview and whatever you do in the webview is accessible to the hosting app. Cookies, bookmarks, etc. are not available to the hosting app.