Enable Application cache in WKWebView

Question

I am aware that offline application cache is not supported in iOS WKWebView.

This is enabled in Safari, so I searched webkit project for the responsible code & found this

WKPreferences

- (void)_setOfflineApplicationCacheIsEnabled:(BOOL)offlineApplicationCacheIsEnabled;

Anyone familiar with this method? is it possible to enable app cache in iOS by accessing this private methods? (I am not going to ship the app to Appstore)

Paradigm

Answer 1

Update 2022

According to one of the comments below, this hack doesn't work anymore.

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Yes, we can enable App cache by accessing private API

Create a category for WKPreferences and add to following method signature.

@interface WKPreferences (MyPreferences)
- (void)_setOfflineApplicationCacheIsEnabled:(BOOL)offlineApplicationCacheIsEnabled;
@end

(I tried performSelector:withObject: but it didn't work. No idea why)

After initializing the WKWebView, enable the appcache by calling the above method in the following object

  [_wkWebView.configuration.preferences _setOfflineApplicationCacheIsEnabled:YES];

It will create the ApplicationCache.db file in the Cache directory and allow the web app to work offline.

Warning :

2.5. Apps that use non-public APIs will be rejected

Paradigm

It's not that they can't, I think that they just won't. My guess is that they want us to handle offline ourselves rather than using the appcache. – Carreon

You got to love Apple for this! – Iaria

Hi Clement, i was wondering if you figured out a way to bypass the 25mb appcache limit imposed (by apple?), if i exceed that i never get the alert dialog asking me if i want to assign more space like in safari and the appcache simply fails to install, maybe there's a way to programmatically define that?, i looked at Webkit source code but couldn't find where they set it. – Mydriatic

@Mydriatic Hello, did you ever find out what the limit was or where it was defined? Thanks :) – Clower

@Clower no, i even asked apple developer support way back then and they simply said it wasn't supported in WkWebView :| – Mydriatic

@Mydriatic ah typical, hehe! Thanks for the quick reply! – Clower

AppCache has been deprecated in all browsers for years and Safari officially deprecated it in 2018. Do not rely on this for anything in 2022. bugs.webkit.org/show_bug.cgi?id=181764 – Agone

Answer 2

According to this tweet from at Apple, as of iOS 10, App Cache is now supported in WKWebView:

https://twitter.com/andersca/status/743259582252879872

...as does this WebKit bug report:

https://bugs.webkit.org/show_bug.cgi?id=152490

I've tested this in WKWebView using this site:

http://webdbg.com/test/appcache/

and can confirm it works as expected both in the iOS Simulator and on devices running iOS 10.

Cajeput

No native-side code changes are required to support App Cache, but obviously you need to make the necessary web content changes. General information about this can be found in Apple's HTML5 Offline Application Cache guide: developer.apple.com/library/content/documentation/iPhone/… – Cajeput

@AndrewEbling Does App Cache cache everything? For example, does it cache AJAX requests and responses? – Carner

AppCache has been deprecated for years and Safari officially deprecated in 2018. Do not rely on this for anything in 2022. bugs.webkit.org/show_bug.cgi?id=181764 – Agone