Browser marketshare is not a constant, it totally depends of your business. At my current job it's: - ~55% Chrome - ~35% Firefox - ~5% Safari - 1.5% IE

Browser marketshare is not a constant, it totally depends of your business. At my current job it's: - ~55% Chrome - ~35% Firefox - ~5% Safari - 1.5% IE 9+10 - 1% Opera So for us it make sense to use API even less supported than WebWorkers, like http://caniuse.com/pagevisibility http://caniuse.com/pagevisibility But if I was working for a chinese market place, or a bank intranet I'm sure it would be 80% IE6.