American Versus European Roulette
Most online casinos offer two versions of Roulette: American and European. The two games have the same payouts on every bet on the felt. At first glance, the games may appear to be identical. That is not the case.
An American Roulette wheel has one additional number on it. It is a second zero displayed as 00. This may seem like an innocent enough difference, but it nearly doubles the house edge. The house advantage on an American Roulette game is 5.26% on most bets. This extra number also creates an additional “First Five” wager not available on single zero wheels. This bet covers 0, 00, 1, 2, and 3. This wager has a house edge of 7.89%. This is one of the worst bets that you will find on any table game outside of the hard ways and hop bets on a craps table.
A European Roulette wheel has just one zero. This makes all wagers on the wheel that pay more than even money have a 2.7% house edge. The even money wagers have a special rule. If the ball lands on zero, the even money wagers receive half of the bet back. A $10 bet would only lose $5. The bets that are covered by this half-back rule are red/black, odd/even, and high/low.
En Prison Rules
Most online casinos simply refund half of an even money wager on a zero. There are some that use the “en prison” rule. This means that the wager receives a second chance. The next spin would determine the outcome of the bet. If the even money bet wins on the next spin, it is returned in full. If it loses, the bet is taken by the house. There are special rules that vary by house about what happens if a zero is called on the follow up spin. In some houses, it will take two wins to retrieve the even money bets. Other casinos simply ignore subsequent zeros and wait until a true number is called to determine the en prison bets.
European Roulette Sometimes Misrepresented
Some online casinos use the term European Roulette incorrectly. These sites will describe any roulette game with a single zero as European Roulette. These misrepresented games will not return half of an even money wager if zero is called. The house edge on even money bets then becomes 2.7%, just as all other European Roulette bets have. The rules on whether a single zero roulette game offers a half-back or en prison rule may be found in the help section of the game. A European Roulette game will either describe the rule in the introduction portion of the help file or mention it on the payouts for red/black, high/low, and odd/even.