can you add a comment pointing to where the 70char max is defined or documented?

also... it'd seem slightly better if you set the const as 70 and do the math.

did not find anything in the docs. I ran into the problem and tested the constraints myself.
I will try to get an official statement in slack?

Sure i can do the calculation starting from the maxChar.

UPDATE:
I found this in the cli tool: https://github.com/zeit/now-cli/blob/c49ba28bbffe74860c845f313882b49c0e85988d/src/providers/sh/util/alias.js#L36

const domainRegex = /^((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}$/

So as i see it we got 63 chars to choose + .now.sh (7 chars) = 70chars