A non-sticky bonus spends your cash first and leaves the bonus untouched. Until your own money runs out, the bonus is sitting in reserve and the wagering requirement has not started.
That single detail changes the whole shape of the offer. You can win on your deposit and withdraw at any moment, because the bonus was never activated.

Sticky against non-sticky
| Non-sticky | Sticky | |
|---|---|---|
| Spent first | Your cash | The bonus |
| Requirement starts | When cash runs out | Immediately |
| Withdraw a win on your deposit | Yes, bonus simply lapses | No, forfeits the bonus |
| The bonus itself converts | Yes, once cleared | Never |
| Worst case | You lose your deposit | You lose your deposit |
The last row is the point people miss. The downside is identical. What differs is how much of the upside you can keep on the way through.
How a session actually plays out
Deposit $100, receive a $100 non-sticky bonus at 35x.
You start with $200 showing, but you are playing your $100. If it doubles to $200, you withdraw $200 and the bonus quietly lapses. Nothing was owed, because nothing was activated.
If the $100 runs out instead, the bonus takes over and $3,500 of turnover begins. You are no worse off than a deposit with no bonus at all, and you have a second run at it.
The same session on a sticky bonus gives you no exit. Any withdrawal before the requirement is finished removes the bonus and everything it won.
What the structure costs you
Nothing is free, and the cost here is time.
The requirement only starts once your own money is gone, which means reaching it takes a full deposit's worth of play. On a sticky bonus the counter is moving from the first spin.
For anyone who plans to stop while ahead, that trade is one-sided in favour of non-sticky. For anyone intending to clear the requirement regardless, sticky gets there sooner.
Spotting one in the terms
The clause reads something like cash funds are used before bonus funds, and it sits near the top of the bonus terms.
Where it is absent, two or three spins settle it. Watch which balance falls. Which pot pays for a spin, and why that matters at conversion, is covered in the bonus balance and the real balance.
Where it sits against no-wagering offers
A non-sticky bonus is a better version of a wagering bonus. A wager-free bonus removes the requirement entirely.
They solve different problems. Non-sticky gives you a large bonus with an escape route. Wager-free gives you a small amount of genuinely withdrawable money. The rare offer that is both is worth taking without much further thought.
If a non-sticky bonus has already activated and the requirement is running, work out whether withdrawing before the wagering is cleared beats finishing it out.