There are two types of progressive jackpot slots: those in which the jackpot is networked (used by many casinos) and those in which the jackpot grows within one or a few online casinos. The prize increases because a certain percentage of every bet that is placed on the game is added to the jackpot. Depending on how popular it is, it will start growing immediately after someone wins. Progressive Slots Jackpot – How Does it Work?Ī progressive jackpot is based on two things: first, it typically has a starting amount, which is a guaranteed minimum win.