There is nothing like a free lunch, and the same applies to welcome bonuses as well. There are many conditions attached to a 1st deposit welcome bonus. For example, the free spins from your 1st deposit bonus will only be redeemable on selected slot games. You will need to meet the wagering requirements before you can withdraw your winnings from the bonus.
While some casinos ask their players to wager only their winnings, some other sites ask them to wager the bonus amount plus the winnings. These bonuses are also available for a very short period and usually expire within 7 days. The maximum bet amount is also reduced drastically, usually around $5. So players should make sure that they read the Terms and Conditions before claiming the casino online offers.