A bonus is not free money. It is a sum you may not withdraw until you have wagered a multiple of it, under rules that vary enormously between casinos. The headline number is the least important part of the offer.
A €100 bonus with 35x wagering means you must place €3,500 of bets before any of it can be withdrawn. On a 96% RTP slot, wagering €3,500 costs about €140 in expected losses — more than the bonus.
That is the calculation almost nobody does, and it is why a large bonus with heavy wagering is frequently worse than a small one with light wagering, and sometimes worse than no bonus at all.
Check whether the requirement applies to the bonus alone or to the deposit plus the bonus. The second doubles the work.
Maximum cashout caps what you can withdraw from bonus winnings regardless of how much you win. A €50 bonus with a 5x cap means €250 is the most you will ever see from it.
Game weighting decides what counts. Slots usually contribute 100%, while blackjack and roulette often contribute 10% or nothing — so clearing wagering on table games can take ten times as long, if it is permitted at all.
A maximum bet while wagering, commonly €5, is the rule that most often voids a win. Exceed it once, even accidentally, and the casino can confiscate the bonus and everything won with it.
Low wagering, no cashout cap, a realistic expiry and slots weighted at 100%. A 20x offer with no cap is usually better value than a 60x offer twice the size.
If the terms are hard to find, that is information too. Every bonus on this site has its wagering and expiry shown on the card, before you click anything.