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Web apps on iOS 4.3 take mysterious performance hit

updated 06:45 pm EDT, Tue March 15, 2011

Is it a bug, an early omission, or a conspiracy?

Testing by developers and The Register has revealed that iOS 4.3 makes changes to the way "web apps" run that significantly impacts their performance compared to fully-native apps or apps run within the MobileSafari browser. In part, this is due to the presence of the new Nitro JavaScript engine, which significantly enhances performance -- but at present only works inside Safari. Other factors that hurt the performance of non-Safari web apps, however, have some wondering if Apple is deliberately deprecating the format to promote its own App Store.

In addition to the unavailability of Nitro for non-Safari web usage, iOS 4.3 also lacks web app caching, even HTML5 application caching, meaning they can't be run offline (although this was actually a change implemented in iOS 4.2). Further, the new version also makes web apps run in "synchronous mode" rather than the newer "asynchronous mode," which can affect graphics performance in full-screen mode. Overall, the bottom line is that web apps run noticeably slower and "choppier" in iOS 4.3 compared to the now-boosted performance of Safari or native apps.

Various conspiracy theorists -- including some developers -- speculate that this could be a deliberate move by Apple to make web apps unattractive, encouraging users to stick to native apps (where, if the app costs money, Apple receives a 30 percent cut). Others believe the changes are simple bugs or oversights that will be addressed in future revisions of iOS 4.3.

The lack of the Nitro Javascript engine outside Safari, for example, is likely to be deliberate -- but perhaps only because it is a brand new feature. After some wide-scale testing, Apple could and likely would make it available outside Safari (since doing so would save space by not having to maintain two Javascript engines).

The dropping of offline caching and keeping web apps in synchronous graphics mode, however, seem more like omissions: the question is whether they are deliberate, or just overlooked in the rush to get iOS 4.3 out. Developers have filed bug reports and spoken with the MobileSafari team about the issues, but no official explanation has yet been issued. The "bugs" also can also affect native applications that use Apple's own UIWebView API to offer "in-app browsers" that act like Safari but actually aren't.

Although some developers in the Register story suggest that Apple will not fix these issues -- at least not immediately -- the impact on native apps that rely heavily on the web for updates (such as UrbanSpoon, Facebook, Ebay and Apple's own MobileMe Gallery app to name just a few) makes it unlikely that the problem will be ignored.

While there is a motivation for Apple to de-emphasize web apps' popularity -- in that they completely bypass the App Store -- commenters on the Register story correctly point out that most "web apps" are free (and a small percentage of the overall app market), meaning no loss of revenue and no real incentive for the company to expend any effort to weaken their limited appeal. Apple's iOS is still the only mobile platform that even offers full-screen web apps, or the option to make a website (such as into a "web app" saved to the home screen.

O'Reilly author Maximiliano Firtman, one of the first to raise the issue, has published tests showing that iOS 4.3 runs web applications in the browser more than twice as fast as those outside the browser, but also posted that he does not believe it is any deliberate attempt by Apple to hinder the hybrid/HTML5 frameworks.

Pictures showing his tests are reproduced below -- in the graphic, the SunSpider JavaScript test is run on an HTML file inside Safari (resulting in an execution time of 4.2 seconds) and then again as a full-screen web app from the home screen (now taking 10.2 seconds to run). His latest update posits that Nitro may be unavailable outside Safari due to security or kernel concerns.

Firtman points out that web apps under iOS 4.3 run at roughly the same speed they did before -- they just don't (yet) take advantage of Nitro, which makes them look slow by comparison to in-browser web apps that do have that benefit. The caching issue and the synchronous mode are other factors that Apple will likely address in developer forums, but as more discussion and testing are done it appears likely that sabotaging full-screen web app performance was more likely an unintentional rather than deliberate act.

However, Firtman suggests that if Apple doesn't quickly address the issues, Google's Android community should -- as it would give them a new area in which to be competitive. [via The Register]

by MacNN Staff



  1. azakel

    Joined: Dec 1969



    Quite personally as a developer I'm glad this happened, i mean sure, there are a few good apps that aren't native (which could be top 10 if they only were), but the difference in performance and more importantly what you can accomplish in terms of presentation and interaction with the user, between a webapp and a native app are humongous and spams the app store with a bunch of half arsed apps that have no business being there in the first place.

    It's like using parallels or vmware to run Wordpad on a virtual machine, there's no point in doing so when you already have textEdit.

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