Ios Uiwebview And Safari Is Not Sending If-none-match But Android Webview And Chrome Does

I am using ASP.NET as server of IOS and Android, which uses ETag and If-None-Match header to return 304 or 200. When I check this on Chrome Dev Tool and remote Debug Android WebVie

Solution 1:

From here,

Caution A few years ago, ETags were used mostly by proxies and not as much by browsers. The value of ETags slowly grows because of the increasing support by browsers. Keep in mind that not all browsers support ETags, though. For example, Apple's Safari does not support them. You may consider providing Last-Modified headers as well and checking for If-Modified-Since headers in addition to using ETags if you expect a large number of of Safari users to visit your site

Solution 2:

Your ETag header field value in syntactically incorrect. Maybe that's why Safari ignores it (which would be good!).

Another reason might be the inability to handle "Vary" correctly (this definitively affects some versions of IE).

Solution 3:

Check this chart to determine if its version specific problem

http://www.yuiblog.com/blog/2010/06/28/mobile-browser-cache-limits/