This kind of bonus is the most common in the online casino world. After your register on a new casino, you are offered a bonus on your first deposit. Sometimes, it is even on your two or three first deposits. It works like this. Let's say you register on a casino that offers a 100% up to €500 welcome bonus (like Wild Sultan for example). You can deposit up to €500, and the casino will give match your deposit at 100%. If you deposit €300, you get €300 as bonus money. €500 being the maximum in this case. The bonus percentage varies from one casino to another. Sometimes you will get a 100%, 150%, 200%, 50% bonus.