The hidden ways mobile sites and free games are killing your battery

You think you know how mobile browsing and games are killing your battery, but it's actually a bunch of unseen inefficiencies.


Chart of mobile website energy usage from Stanford study

Chart via "Who Killed My Battery?"; click for larger view

You know about some of the things that are putting such a hurt on your mobile battery that you can’t hit 4 p.m. without a warning. Streaming music over 3G, for example, or keeping the screen on for long camera sessions. But mobile web sites and certain free apps might be killing your phone’s juice in sneaky ways, according to some recent studies.

At the World Wide Web 2012 conference in Lyon, France, this week, Stanford researchers plan to present “Who Killed My Battery?: Analyzing Mobile Browser Energy Consumption” (PDF link), a study of how much power is consumed by mobile browsers on popular websites. They hooked up an Android phone and its battery to a rather geeky-looking monitor, and started surfing the mobile web. Even among those sites that offer mobile-optimized versions, there were some serious battery killers in the crowd: Wikipedia, Tumblr, IMDB, and Blogger, among others.

The main culprits are cascading style sheets (CSS) and JavaScript, which need to be downloaded and parsed by the mobile browser. On Wikipedia’s mobile site, the researchers actually modified the page scripts themselves, and came up with a version that reduced energy usage by around 30 percent, without any change to the content itself. Image formats (using JPG instead of GIF or PNG) make a difference, too, but the real difference is in how you handle interaction. The site that came out looking slim and powerful was Gmail’s mobile site, which uses HTML-based scripts to create an app-like experience, caches what information it can on the phone, and pares everything down for lower processing and data radio demands.

What would really help, the researchers suggest, was if more sites offloaded some of the computation, script-handling, and image scaling to their own servers, rather than asking your phone to handle it. Stanford researchers suggest both front-end proxies (which intercept data from web servers and render them in optimized form for the phone, as on Opera and Skyfire mobile browsers) and back-end servers (which the phone sends data to for processing). And if Google Analytics would allow mobile sites to be cached on the phone, instead of demanding fresh versions on every view for traffic-measuring purposes, that would help a lot, too.

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