Online casinos are falling over themselves to get you to sign up, and one of the ways they get you to do it is to offer bonuses. Many bonuses aren't worth taking, but some definitely are. How to know when a bonus is worth taking? Simply calculate the expected value, given the wagering requirement, house edge, and bonus amount. For example, suppose you're offered a bonus of £50 and the wagering requirement is x 20, meaning that you must wager 20 x £50 = £1000. Is this a value bet? You may be restricted in the games you can play to meet the requirement, but let's suppose you can play standard single zero roulette (obviously you should pick the game with the lowest house edge).

The expectation is that you will lose 0.027 * £1000 = £27. Subtract this from the bonus and you're left with £23, therefore this bonus is worth taking. Remember this isn't a no risk bet because the expectation is an AVERAGE, meaning that "in the long term" it's favourable because the expectation is positive, but it's possible, because of variance, that you will lose MORE than £27. You may even lose the entire bonus amount (although unlikely).

Here's a calculator which will tell you whether any casino bonus is worth taking

https://www.bankofbets.com/ev-calculator