[youtube http://www.youtube.com/watch?v=UQAPtfVaVDA&w=560&h=349]

Google's Steve Souders says the big fail point for most mobile apps is they load way too much Javascript. He was speaking at a presentation at Silicon Valley Code Camp on how to make your mobile apps faster with HTML5. The reason most apps slow to a crawl is they’re not loading Javascript asynchronously, and they’re letting the mobile browser parse and execute all that code. If you do that, the UI thread locks so the user can’t interact with the app. “You don’t need to parse and execute (the HTML5 stuff) until the user enables that feature,” he says. The solution to speeding up your HTML5 app on mobile browsers is to have it load Javascript asynchronously, and not to parse and execute until you really need to. It will actually make the UI much more responsive. Other techniques Souders recommends is using the app cache or local storage because browser caches are very small. Also, reduce your image sizes using something like Sencha.io. There’s no need to download images that are bigger than the mobile screen. For lots more advice, check out Souders’ blog at SteveSouders.com.