Google does a lot of A/B testing, called Experiments. YouTube has some cool tools for QA testing those experiments... This redesign is being A/B tested (with h

Google does a lot of A/B testing, called Experiments. YouTube has some cool tools for QA testing those experiments... This redesign is being A/B tested (with high percentages of users it's rolled out to). It comes in different parts, so if you clear your cookies and reload you can be reassigned a bucket and therefore see slightly different interfaces. Bonus: I think the redesign is called called Amsterdam, don't quote me on that though...