When it’s free
Four equal payments, paid on time, no interest. Genuinely free money compared to a credit card. Klarna’s ‘pay in 4’ is the cleanest version.
When it’s a trap
Miss a payment by one day, retroactive interest on the original amount. Sometimes also a late fee. Affirm has tiered offers — read the fine print every single time.
Sane usage
Set autopay. Don’t use it for anything you couldn’t afford in cash today. The default-to-debt habit is what they’re cultivating.