WKWebView

WebView (on Mac) is the old WebKit view that runs entirely in-process. WKWebView is the new hotness that runs in its own process, for performance and security (so they claim). It has a number of rather significant downsides which made it useless to me for the first several years. Even in 2020, it lags WebView in features, in many ways:

• It ignores custom [NS]URLProtocols. It'll load the protocol and claim to support it, but then ignore it completely.
  • In 10.13, there's a WKURLSchemeHandler! Note that the interface is completely different -- this means re-architecting, not just updating some method names.
• Xcode 8 can't add it in IB. (FB5550470)
  • Xcode 9 can! ... sort of.
• You get a "Reload" context menu (and "Open in New Window", etc?), and it's not easy to disable (FB8653798)
• Printing is broken (36557179)
  • macOS 11 beta added this!
• No way to use a user stylesheet (37652333)
• To set any configuration on it (like a WKURLSchemeHandler), you need to pass that configuration to its init, which means you can't create it in IB. (FB8653162)
• Requires the security.network.client entitlement even for displaying static text. (FB8653139)
• webView:stop: is only called for loading cancellations, i.e., usually never. There’s no easy user “cleanup” point for tasks.
• The stack traces you get from WKWebView-related crashes are pretty awful. Mangled names.
• When you call setURLSchemeHandler, if the scheme is built-in, you get an exception. You're supposed to use WKWebView.handlesURLScheme to check first (and keep adding suffixes or something until you find a free one?). In their WWDC video, they say to prefix it with your company name, like “apple-local” (instead of just “local”). There’s no built-in way to say “give me something which I'm free to use”.