Types of No Deposit Bonuses
There are a variety of no deposit bonuses in disguise. Free spins are considered a no deposit bonuses since they are awarded for simply registering your information and creating an account. Also, free tournaments offer you the opportunity to play in a real money tournament without the buy-in. Again, there will be withdrawal requirements should you win. Free play is another type no deposit bonus which essentially give you a free opportunity to play, no strings attached.
Another important point found in most T&C is that you must deposit to withdraw any winnings associated with the bonus. This makes sense in that the casino does not want you to sign up, win with no personal risk and then never return.
These are a variety of other T&C's that are not listed but the three points are the most common. For more specific terms, contact your casino of choice or check the bonus terms section on their website.
For those who receive the no deposit bonus just for being a valued player at that casino, there are T&C that must be met including limited immediate withdrawal without making a deposit or meeting a point requirement. In this instance, everybody wins: the player can play with free money and the casino is contributing to the player continuing to play. Without this free promotion, they may have otherwise left the site.