massive memory leak in ios UIWebView

Asked 13/5, 2013 at 2:52 Answered 18/2, 2015 at 14:59

ios memory uiwebview refresh memory-leaks

looking for mem leaks elsewhere in our system, I created a 20 MB web page with a meta refresh tag. the idea was to move a lot data through our datapath code to confirm mem stability.

<html>
<meta http-equiv="refresh" content="1">
<body>
<div style="border: 1px solid red">
    Content loading
</div><!-- 20mb worth of comments -->
</body>
</html>

what I found was the uiwebview displaying that meta refresh page leaks memory very, very fast. the app memory hits 300mb in about 2 minutes and gets shot on a low mem warning, even when our code is not in play.

I have stopped the refresh loading and tried to dealloc the webview.

I have tried loadurl:"about:blank", loadhtml:"", javascript document close.

I also tried writing a recursive removeFromSuperview and removeFromParentViewController, reading that the private scrollview in the webview is a memory problem, but that memory is never freed. I can't seem to find a reliable way to close, dealloc a webview when we are done with it.

We have lived with a slow rate of webview leaking for quite a while and really want to find a way of assuring a webview can be fully cleaned up when we are done with it. We recently converted the app to ARC which did not change the memory rate.

I am considering trying a recursive loop through all the objects in the webview and see if they can be freed. instruments shows 20 mb of cfdatas, alive, for each refresh of the 20MB page, but does not show them as leaks. if i only deliver the response header and done to the urlprotocol client we run stably so was ale to confirm the memleaks in the rest of the data path, but this is such a dramatic test case result am hoping to find a webview mem leak solution once and for all.

Does any one have any better ideas or has anyone tried recursing through the objects in a uiwebview?

Hawkbill answered 13/5, 2013 at 2:52 Comment(1)

When the app shows no leaks, but growing data, that means that the objects are alive somewhere. Find them (go through their retain / release history in instruments) – Pierson 13/5, 2013 at 2:56

The way I got rid of my UIWebView's memory leakage is by setting its HTML to the empty string. One place to do this is when the view controller containing the web view disappears:

- (void) viewWillDisappear:(BOOL)animated {
    if (self.isMovingFromParentViewController) {
        [self.wv loadHTMLString: @"" baseURL: nil];
    }
}

Linettelineup answered 13/5, 2013 at 2:59 Comment(4)

This helped me reduce the leak, but did not fix the problem completely. Thanks for sharing your solution, though. – Clayton 9/8, 2014 at 21:11

@Clayton Don't forget to set the web view's delegate to nil as well. – Linettelineup 9/8, 2014 at 21:24

Yep, I have that in as well, doesn't help much. – Clayton 10/8, 2014 at 2:52

This in my case fixed the memory leak! – Lynseylynus 9/6, 2016 at 8:8

A shout to all developers: Implementing didReceiveMemoryWarning is an absolute must when using a UIWebView!

And it's specially important when the UIWebView can navigate anywhere or to a page you know that causes UIWebView to have huge leaks, such as m.youtube.com.

A great and usually seamless way to fix the leaks is just reloading the page. In that way you don't need to care about the page becoming empty, and usually the user will be able to continue its work from where he left off.

In your view controller, override didReceiveMemoryWarning like this:

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    [myWebView reload];
}

Potherb answered 26/10, 2013 at 16:48 Comment(1)

I just tried this. This caused the UIWebView to reload multiple times uncontrollably, but failed to keep memory growth in check. Should I have been more patient? – Domineer 1/9, 2015 at 18:45

With iOS 8 and onwards, you are really in luck. WKWebView does not leak and has a much smaller memory footprint than UIWebView. Having tested it with image laden web pages containing complex Javascript, it performed well.

Apple's WKWebView Class Reference

nshipster on WKWebView

It's not perfect though. Then again hopefully imperfections will be resolved in time. Check out Shingo Fukuyama's tips on GitHub:

WKWebViewTips

Backwater answered 18/2, 2015 at 14:59 Comment(2)

this is great on iOS 8, but so many of us still must support iOS 7. and so many of us have tried the solutions offered with no luck on iOS 7. very frustrating – Vere 30/3, 2015 at 16:28

Unfortunately this isn't necessarily true. I'm not 100% sure if it is this way on iOS 8, but on iOS 9, wkWebView leaks memory all over the place. Just a heads up for anyone who decides to switch to wkWebView based on this. References: forums.developer.apple.com/thread/22795 and forums.developer.apple.com/thread/21956 – Soandso 18/8, 2016 at 13:52

-1

Weakify "self" in the blocks.

This was one of the important reasons that lead to holding up of WebView memory even when popped out the navigation stack.

Hurtle answered 25/11, 2014 at 5:52 Comment(0)

A shout to all developers: Implementing didReceiveMemoryWarning is an absolute must when using a UIWebView!

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