A sign up bonus is credited when a new account completes a specific trigger. That trigger can be registration, verification, a first deposit or a first settled bet.
The trigger defines the offer's real cost. Registration-only bonuses cost nothing but are small. Deposit-triggered bonuses are larger but tie up cash. Bet-triggered offers need a qualifying wager at set odds.
Most sign up offers also need an activation step. That might be a promo code, a tick box during registration or an opt-in button in the promotions tab. Editorial tests found this step to be the most common reason bonuses go missing. A forgotten opt-in rarely gets fixed after the deposit.
"Sign up bonus" and "welcome bonus" often describe the same offer. The difference lies in focus: sign up offers stress the registration trigger. A broader comparison of formats sits in the betting offers guide.