Online slots make up one of the biggest sectors of casino gaming, and they are a lot more diverse than their older mechanical counterparts. They can range in themes, number of reels, payout rates and the types of features they offer. Some of them even have bonus events and varying levels of skill-based gameplay. Despite this diversity, they have to stick to the same basic principles as all other gambling games. They take money in, they spin and they should spit some of it back out, regardless of whether you win or lose.

The most common type of slot online is the video slot, which can be played on desktops, mobile phones or tablets. These typically have 5 to 7 reels and multiple paylines. Some are based on classic slot themes such as the Mystery Zone from NetEnt or Book of Ra, while others are inspired by popular TV shows and movies. They usually also have a wild range of bonus features, from pick-a-prize rounds to progressive jackpots.

Unlike the electromechanical machines in casinos, which are programmed to give the house an edge, newer electronic versions of these games use random number generators to determine the symbols that appear on the reels. This process is regulated and audited by independent expert agencies to ensure that it is fair and unbiased.

Players can adjust their bets by choosing the coin size, number of coins per payline and the number of active paylines. The game software then calculates the total cost of a spin and displays it on the screen. A good rule of thumb is to always activate all paylines unless you’re playing a game that specifically requires you to do otherwise.

Another factor to keep in mind is the slot’s payout percentage, which indicates how much it should return to players over time. This value is posted on the rules or information page for each game, and is usually calculated and displayed as a percentage. It’s important to compare this percentage with other slots in the same category, as some may have higher or lower returns than others.

Some online slots have progressive jackpots, which grow each time a player places a bet and are reset when the jackpot is hit. These jackpots are not guaranteed to be won, and they can vary in size depending on the game developer and the specific slot. These types of slot machines can be found on sites operated by leading casino software developers like Microgaming, Playtech and NetEnt.

Another popular type of slot is a branded game, which uses licensed characters and content from famous movies, television series, sports celebrities or rock bands. These can be developed through licensing agreements with content providers or in-house by the gaming operators themselves. These slots are often the largest source of revenue for casinos, and they also have the potential to attract a larger audience than unbranded titles. This is because of the familiarity of these brands with audiences.