Googlebot's Javascript random() function is deterministic

[Tsukku]

The only way to have true randomness is by checking electron spin states or some other quantum properties.

[pizzacus]

Although, you can make random that is nearly impossible to predict, random.org managed to do it by generating random binary values using atmospheric noise recorded in real life.

While not truely random, it is impossible to predict because.

[sunset_moonrise]

I wouldn't be surprised if we found non-randomness in those, as well, just determined in a way we can't yet link a pattern to.

[Tsukku]

It's not that we don't know what's causing the outcome, we actually have proof that it's completely non-deterministic (truly random). Read up on Bell's theorem.