When I drag a UIWebView from the Object Library in Xcode, I get a UIWebView with this dark grey bar at the top:
What is that and how can I get rid of it?
You need put self.automaticallyAdjustsScrollViewInsets = NO; in ViewDidLoad
The other choice is disable option Adjust Scroll View Insets in the .xib of your viewcontroller
That dark grey color is the background color set for the UIWebView. This will show if a webpage is smaller than the frame of the web view. You won't see it if you change the background color to white or transparent.
_webView.scrollView.contentInsetAdjustmentBehavior = .never
This should work if you have a WKWebView/UITableView/ScrollView. Add this in ViewDidLoad. This will make the status bar overlap the content without adding a extra white space in the status bar.
来源：https://stackoverflow.com/questions/41623507/grey-bar-on-top-of-uiwebview-in-ios-10