Avalanche vs snowball, on your debts

Avalanche targets the debt with the highest APR. Snowball targets the smallest balance. Both pay every minimum first, then throw the extra payment at the one target debt.

When a debt reaches zero, its minimum payment rolls into the next target. Your total monthly payment stays the same, so each payoff makes the next one faster. That rollover is the whole engine of both methods.

Avalanche almost always costs less in interest. Snowball almost always scores the first win sooner. The cheaper method only wins if you stick with it, so the right pick is the one you will keep doing.