In my testing it does not appear that having the size params out of order (where the order is size-width-height) actually works with Google's user content static hosting. The single params usually work, and all together usually work, width-height usually works, but otherwise, only the first param is respected (ie: w700-s2560 gives the same result as just w700, etc). So this regex is way more complicated than any of our (admittedly assumed space of) inputs will be. The original regex or something similar does the job without complicating the problem.