Online casinos draw in plenty of players advertising what sound like huge and absurd prizes: “Win £750,927.21 or more!” You might even see the total slowly ticking up penny by penny.

This is what’s known as a progressive jackpot, which is a type of jackpot (a big win) which increases over time as more money is put into the game. They are common on many video slot games and table games such as Blackjack and Roulette. Lotteries often use the term ‘rollover’ to mean the same thing.

But what is going on here? Is this your chance to win big, or is it impossibly unlikely? We’re here to answer these frequently asked questions. 

How does a progressive jackpot work?

On a progressive game, the winnable jackpot will rise incrementally as players put money into the game. Every time money is wagered and not won, the game contributes a small percentage of the amount played to the jackpot. This is why the jackpot on these games are called ‘progressive’ – unlike a classic game, the prize is not a fixed amount, it is continuously growing.

When somebody wins, the jackpot is reset or ‘reseeded’ to its predetermined value and resumes increasing as players continue to bet. The greatest progressive slots may reseed their jackpots to £1million.

How big can a progressive jackpot payout become?

This depends on the game you choose. There are two types of progressive jackpots. One is local, which means an online casino grows the jackpot according to all of the players playing the game on its site.

The other is a networked progressive slot. This is when a game provider pools a percentage of all bets on a game from players across potentially hundreds of online casino sites for the jackpot total.

These are much more common as the more players contributing to the jackpot, and the larger the jackpot, the easier it is to market and bring in even more players. 

Fun fact! The record for the largest progressive jackpot was broken on 28 September 2018, when a player won a total of £22.3 million on Microgaming slot game Mega Moolah. The winner was an anonymous Android mobile device player, who staked 75p on Mega Moolah and less than 50 spins later landed the jackpot. Now just imagine if they landed that on free spins!

How likely am I to win a progressive jackpot?

The positive is that progressive jackpots give you the chance to turn a tiny stake into a giant multi-million pound prize.

But the negative is that the offs of winning the top jackpots are literally more than a million to one. Some games offer odds of 1 in 150 million to 1 in 300 million.

All of those millions of bets have the same chance of winning! It could be yours.

Jackpot prizes can be won at random after any spin as they are governed by random number generators (RNGs). The mechanics go like this: every time you spin, a set of random numbers is chosen. If you happen to get the right one, you win!

Remember that it’s impossible to play your way to the top strategically. A progressive jackpot that hasn’t been won in a long time will attract the attention of lots of players, meaning the prize will increase at a faster rate. But even if a jackpot has gone unclaimed for weeks, there’s no reason it will be suddenly ready to drop.

This is even true of ‘must-drop’ jackpots. These have a strict deadline by which they must be won, so they attract more players and the prize grows more rapidly as the date approaches.

Many casinos have rules in place that mean you are only eligible to win the prize if you are betting the maximum wager possible. Be sure to read the game’s terms and conditions to be sure you’re in for a chance to win.