All casino promo codes are free to use (e.g. you won’t need to pay to access any). But you might need to make a deposit to trigger the bonus. Take a look at the following examples:
No Deposit: If you come across any no deposit bonus codes, they are completely free to use. Just sign up and quote the necessary letters and numbers to grab free bonus money or free spins.
Deposit: On the other hand, your codes may only take effect after making a deposit. These are useful for unlocking larger offers (e.g. 200% rather than 100%).