Is WKWebView designed as a replacement of UIWebView?

As per Apple Developer site:

If your app still embeds web content using the deprecated UIWebView API, we strongly encourage you to update to WKWebView as soon as possible for improved security and reliability. WKWebView ensures that compromised web content doesn’t affect the rest of an app by limiting web processing to the app’s web view. And it’s supported in iOS and macOS, and by Mac Catalyst.

The App Store will no longer accept new apps using UIWebView as of April 2020 and app updates using UIWebView as of December 2020.

Update: UIWebView is now deprecated and Apple is actively discouraging developers from using it.

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There are several reasons, including security (out of process model), performance and memory management. Whether Apple would deprecate UIWebView is not something anyone can answer but Apple, however considering the many limitations there currently are (some partially solved in WebKit2 source repository for future iOS WK2 framework inclusion), my educated guess would be that UIWebView is here to stay for different needs. And considering both WebKitLegacy and WebKit2 (now renamed WebKit) frameworks reference the same implementation frameworks (WebCore, JSCore, etc.), it would not require a lot of work to keep UIWebView alive.

According to Xcode 9, UIWebView is deprecated. 🤷‍♂️

And a documentation message reads:

Legacy UIWebView for support of older macOS platforms. Prefer using WKWebView if possible.

Updated: UIWebView is deprecated for real now in iOS 12. https://developer.apple.com/documentation/uikit/uiwebview