On a French or European single-zero roulette table that offers the en prison rule, an even-money bet doesn't lose outright the moment the ball drops into the green zero.
Instead, the bet is imprisoned: held in place for one more spin, which decides whether the stake comes back or is lost. The rule applies only to even-money bets, and where it does, it cuts the house edge from 2.70% to 1.35%.
How a Spin Plays Out
Say you place a $10 bet on red, and the wheel lands on zero. Under en prison, the roulette dealer doesn't sweep the $10 away. A marker goes on the chip instead, and the bet sits imprisoned for the next spin only.
If that next spin lands on red, the imprisoned $10 comes back to you. There's no profit on it, since the imprisonment spin pays nothing extra, but there's no loss either. If the next spin lands on black, the imprisoned $10 is taken and the round closes.
A second zero while the bet is imprisoned is its own case, covered in the FAQ below.
En Prison vs La Partage
La Partage works differently. Instead of holding the bet for another spin, the table returns half the stake immediately when zero hits, and the round ends there.
Both rules bring the house edge on even-money bets down to the same 1.35%, since giving back half a losing stake works out mathematically the same as a 50/50 shot at getting it all back next spin.
It's fixed by the table itself, alongside the broader roulette odds and payouts for every other bet type, so it's worth checking before you sit down if the difference matters to your session.
Which Bets Qualify
En prison only protects even-money bets: red or black, odd or even, high or low. Inside bets, a straight-up number, a split, a corner – none of them is covered. If zero lands on an inside bet, the stake is lost in full, no imprisonment involved.
Not every table runs this rule either. It's most common on French-style layouts and largely absent from American double-zero wheels, and the split between French, European and American roulette tables decides a lot more than just this one rule.
Check the table's rules panel, or ask the dealer, before assuming en prison is on offer.
The En Prison Rule – FAQ
Can a bet be imprisoned twice?
On some tables, yes: if zero lands again while a bet is already imprisoned, it can be imprisoned a second time instead of being settled outright.
Other tables release the wager or apply their own house rule at that point instead, so it's worth checking a table's specific rules if this matters to you.
Can you leave the table while a bet is imprisoned?
In practice, no. Since the imprisoned bet settles on the very next spin, you're waiting at most one round, and a live table won't let you walk away with an open, unresolved bet on the layout.
Online, the same logic applies: the spin has to resolve before the round closes.
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