How to determine the content size of a UIWebView?

It turned out that my first guess using -sizeThatFits: was not completely wrong. It seems to work, but only if the frame of the webView is set to a minimal size prior to sending -sizeThatFits:. After that we can correct the wrong frame size by the fitting size. This sounds terrible but it's actually not that bad. Since we do both frame changes right after each other, the view isn't updated and doesn't flicker.

Of course, we have to wait until the content has been loaded, so we put the code into the -webViewDidFinishLoad: delegate method.

Obj-C

- (void)webViewDidFinishLoad:(UIWebView *)aWebView {    CGRect frame = aWebView.frame;    frame.size.height = 1;    aWebView.frame = frame;    CGSize fittingSize = [aWebView sizeThatFits:CGSizeZero];    frame.size = fittingSize;    aWebView.frame = frame;    NSLog(@"size: %f, %f", fittingSize.width, fittingSize.height);}

Swift 4.x

func webViewDidFinishLoad(_ webView: UIWebView) {    var frame = webView.frame    frame.size.height = 1    webView.frame = frame    let fittingSize = webView.sizeThatFits(CGSize.init(width: 0, height: 0))    frame.size = fittingSize    webView.frame = frame}

I should point out there's another approach (thanks @GregInYEG) using JavaScript. Not sure which solution performs better.

Of two hacky solutions I like this one better.

I have another solution that works great.

On one hand, Ortwin's approach & solution works only with iOS 6.0 and later, but fails to work correctly on iOS 5.0, 5.1 and 5.1.1, and on the other hand there is something that I don't like and can't understand with Ortwin's approach, it's the use of the method [webView sizeThatFits:CGSizeZero] with the parameter CGSizeZero : If you read Apple Official documentation about this methods and its parameter, it says clearly :

The default implementation of this method returns the size portion of the view’s bounds rectangle. Subclasses can override this method to return a custom value based on the desired layout of any subviews. For example, a UISwitch object returns a fixed size value that represents the standard size of a switch view, and a UIImageView object returns the size of the image it is currently displaying.

What I mean is that it's like he came across his solution without any logic, because reading the documentation, the parameter passed to [webView sizeThatFits: ...] should at least have the desired width. With his solution, the desired width is set to the webView's frame before calling sizeThatFits with a CGSizeZero parameter. So I maintain this solution is working on iOS 6 by "chance".

I imagined a more rational approach, which has the advantage of working for iOS 5.0 and later... And also in complex situations where more than one webView (With its property webView.scrollView.scrollEnabled = NO is embedded in a scrollView.

Here is my code to force the Layout of the webView to the desired width and get the corresponding height set back to the webView itself:

Obj-C

- (void)webViewDidFinishLoad:(UIWebView *)aWebView{       aWebView.scrollView.scrollEnabled = NO;    // Property available in iOS 5.0 and later     CGRect frame = aWebView.frame;    frame.size.width = 200;       // Your desired width here.    frame.size.height = 1;        // Set the height to a small one.    aWebView.frame = frame;       // Set webView's Frame, forcing the Layout of its embedded scrollView with current Frame's constraints (Width set above).    frame.size.height = aWebView.scrollView.contentSize.height;  // Get the corresponding height from the webView's embedded scrollView.    aWebView.frame = frame;       // Set the scrollView contentHeight back to the frame itself.}

Swift 4.x

func webViewDidFinishLoad(_ aWebView: UIWebView) {    aWebView.scrollView.isScrollEnabled = false    var frame = aWebView.frame    frame.size.width = 200    frame.size.height = 1    aWebView.frame = frame    frame.size.height = aWebView.scrollView.contentSize.height    aWebView.frame = frame;}

Note that in my example, the webView was embedded in a custom scrollView having other webViews... All these webViews had their webView.scrollView.scrollEnabled = NO, and the last piece of code I had to add was the calculation of the height of the contentSize of my custom scrollView embedding these webViews, but it was as easy as summing my webView's frame.size.height computed with the trick described above...

Resurrecting this question because I found Ortwin's answer to only work MOST of the time...

The webViewDidFinishLoad method may be called more than once, and the first value returned by sizeThatFits is only some portion of what the final size should be. Then for whatever reason the next call to sizeThatFits when webViewDidFinishLoad fires again will incorrectly return the same value it did before! This will happen randomly for the same content as if it's some kind of concurrency problem. Maybe this behaviour has changed over time, because I'm building for iOS 5 and have also found that sizeToFit works in much the same way (although previously this didn't?)

I have settled on this simple solution:

- (void)webViewDidFinishLoad:(UIWebView *)aWebView{            CGFloat height = [[aWebView stringByEvaluatingJavaScriptFromString:@"document.height"] floatValue];    CGFloat width = [[aWebView stringByEvaluatingJavaScriptFromString:@"document.width"] floatValue];    CGRect frame = aWebView.frame;    frame.size.height = height;    frame.size.width = width;    aWebView.frame = frame;}

Swift (2.2):

func webViewDidFinishLoad(webView: UIWebView) {    if let heightString = webView.stringByEvaluatingJavaScriptFromString("document.height"),        widthString = webView.stringByEvaluatingJavaScriptFromString("document.width"),        height = Float(heightString),        width = Float(widthString) {        var rect = webView.frame        rect.size.height = CGFloat(height)        rect.size.width = CGFloat(width)        webView.frame = rect    }}

Update: I have found as mentioned in the comments this doesn't seem to catch the case where the content has shrunk. Not sure if it's true for all content and OS version, give it a try.