iOS 5 Catches Up to Android, Windows Mobile Apple fans hoped for a completely new iPhone 5. Instead, they got the same form factor with promises of improved performance. The mobile performance experts at put iOS 5 through its paces and the results are encouraging but far from revolutionary.

With a major revision of the mobile operating system comes a corresponding major revision of the iPhone's browser. The number-crunchers at Blaze have been testing the new browser for awhile but could not share the results due to Apple's silly little NDA.

Before we get into the good news and the not-so-good news, it's important to know that iOS 5 includes 3 browsing experiences:

  • Mobile Safari -- the standard iPhone browser
  • Home Screen Pages -- pseudo-apps that are added to the home screen via Mobile Safari
  • UIWebView -- browser component used within apps such as Twitter and Facebook


To begin with, Blaze offers a comparison of iOS 4 and iOS 5 across 10 categories:

Browser Performance Highlights
Browser Performance Highlights

The Good News

The biggest improvement by far is in rendering performance, thanks to the addition of a graphics processing unit (GPU). To demonstrate the importance of performance when running predefined graphics actions -- what GPUs are designed to do -- Microsoft created a test called "HTML5 Speed Reading" to tout the speed of IE 9 mobile.

iOS 5 runs the "HTML5 Speed Reading" test at 40 frames per second (FPS), while iOS 4 runs the same test at 2 FPS. Take a look at the following video to see a 2000% speed improvement:

Blaze: iOS 5 vs iOS 4 Speed Reading Test from mikeweider on Vimeo.

Another addition to all three browser flavors of iOS 5 is HTTP pipelining. HTTP pipelining is a technique where multiple HTTP requests are sent on a single HTTP connection without waiting for the corresponding connections. This technique helps to deal with the long latency that mobile networks suffer from.

While the addition of HTTP pipelining is nice, it's important to remember that the Android and Opera mobile browsers have supported the technique for awhile now. It's also important to remember that Blackberry still doesn't support HTTP pipelining, as if you needed another reason to not by a Blackberry.

The Bad News

As you can see in the table above, one area where browser performance actually degraded is using Javascript within UIWebView. One could argue that a major upgrade like iOS 5 should not take any steps back in performance. It remains to be seen if this area will be addressed in an upcoming point release.

Also, iOS 5 rolled back a feature from iOS 4 that supported the parallel downloading of CSS files. In other words, image files won't start downloading in iOS 5 until all the CSS files are finished downloading. I can hear the collective groan of mobile web developers everywhere.


While the upgrade is not revolutionary or perfect, it is an overall improvement and most important -- it's free. Users can expect slight improvements in the browsing experience and developers have a few new tools to improve the performance of their apps and sites.

Do you have iOS 5 on your iPhone or iPad? If so, drop us a comment and let us know your thoughts on the latest version of the mobile OS.