The consent has to be explicit. Of course, you can always just require consent in order to sign up. Just as long as it's clear what's going on and you can remove/anonymise the data if the user decides to revoke their consent and leave the service.
OK, but explicit in what sense? Does it have to refer to the GDPR, as in "I agree my dta will be stored according to GDPR"? I must admit I have trouble understanding it - how could anybody sign up anywhere without data being stored?
