When you play slot online, you have to remember that the results of each spin are based on random numbers generated by software. This means that even if you know everything about the game’s symbols and paylines, you still have no control over whether or not you will win. That’s why it is important to choose a casino that is licensed and audited by reputable testing agencies.

While there is a huge variety of different slots available online, they all have one thing in common: they are based on random number generators (RNG). The RNG produces random numbers that correspond to the positions of symbols on the reels after each spin. These are then compared to theoretical projections to determine if the slot is fair or not. While the RNG is the only thing that determines the outcome of a spin, there are other features that online casinos can add to make the games more interesting.

Some slot games have cluster pays, which replace traditional paylines with a single payline that runs horizontally across the reels. This system is popular with Microgaming, which uses it in many of its titles. Another feature is tumbling symbols, also known as avalanches or rolling reels. These features make winning combinations more likely by removing existing symbols and allowing new ones to fall in their place from above.

Another feature that online casinos often use is a progressive jackpot, which increases with each bet and can be won at any time. Usually, this is achieved through a combination of symbols or by activating a bonus game. Other times, a player may just hit the right symbol to unlock it.