The bonus is free. The rollover is not.
A casino bonus looks like a gift. The wagering requirement is where the gift quietly goes back. Enter the terms and see the real number — and whether the bonus comes out ahead or is bait.
The idea
Read the rollover before the amount.
A 100 bonus with a 35x rollover forces you to wager 3,500. Over that volume the house edge of whatever game you play eats into the bonus — and very often eats all of it. The headline amount is the bait; the wagering requirement is the price.
What a bonus costs
The bonus is free. Clearing it is not. See the real number.
How many times the bonus must be wagered. 30x, 40x...
Slots usually 100%, roulette and blackjack 10-20%.
Slots ~4%, European roulette 2.70%, blackjack 0.5%.
You have to wager
3,500 €
Real volume, adjusted for contribution
Expected cost of clearing it
140.00 €
What you lose on average wagering that volume
-40.00 €
Clearing the bonus costs you 140.00 € on average, more than the 100 € of the bonus itself. The 'gift' ends up costing you: the rollover is designed for the casino to win.