Some crypto sites offer promo codes to get a little bit extra crypto. Usually they give this in extra coins or rolls.
Most of the time, the offer of promo codes is limited for a specific number of users (first come first served) or only valid at the day of publishing.

I try to collect as much as possible for you, so you can check all these promo codes. If I missed a promo code, just drop me an email and I try to add it as soon as possible.