Apple’s iPad and Web Caching
Like most tech folks, I spent the afternoon watching and reading about Apple’s new iPad. To call it beautiful and innovative is an understatement. I want to purchase one. As in, right now. At $500 price point I wouldn’t even consider buying a netbook. Since I already have a netbook, I’m seriously considering replacing it with an iPad because web browsing looks amazing on the iPad. After all Steve Jobs himself promised me “It is the best browsing experience you’ve ever had.”
Only I’m not sure if that’s true.
Web Performance on the iPhone
We always talk about web performance as something that only the site owners care about. Few people talk about web performance when it comes to choosing a browser. Certainly no one talks about choosing a browser based on simple performance features like which one supports compression, or caching, or conditional requests, or resumable downloads. That’s because this isn’t 1997 and all the browsers do these basic features equally well.
Only I am sure that’s not true.
Stoyan Stefanov wrote an excellent and detailed article on how the cache for Safari on the iPhone works, or rather, doesn’t work. You should read the entire article. For this article we are most interested in two shortcomings of iPhone Safari’s disk cache that severely impact the browsing experience.
Resources > 15K aren’t cached.
Total Cache Size is only 1.5 Megs.
The moral here is that 1.5 megs of cache is just way too small to be helpful. Furthemore, the cache can get cleared inadvertently several ways, such as closing Safari without certain tabs or some types of powering the iPhone up and down. This means the meager assistance the cache provides can be undercut
These two limits means the disk cache for Safari on the iPhone can reasonably store a few hundred objects. How quickly does that fill up? Of the 32 images on the main page of CNN right now, 29 of them are less than 15K and would get cached. (Ironically the photo of Steve Jobs holding an iPad is too large to be cached).
“It is the best browsing experience you’ve ever had.”
The long and short of it is the version of Safari that runs on the iPhone is just awful when it comes to caching. And as we know, the fastest request a browser can make is none at all. As such caching is a important aspect of web performance optimization, caching directly affects page load times, and caching is critical to the end user’s web browsing experience.
So far, it seems like much of the iPad is running the iPhone OS with the iPhone apps. If this is the case than I am not hopeful about the web browsing experience on the iPad. If Apple is really going to give “the best browsing experience you’ve ever had” they simply must improve the web caching for Safari on the iPad. Otherwise the iPad will be like a DeLorean when it comes to web browsing: beautiful, but underpowered.
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