The first words came to me was pops or poppers (it turned out that only the latter is common). However, googling for pop firecrackers, I found things like Pop Pop Firecrackers, Pop Pop Snappers, along with this Wikipedia page: Bang snaps,
Bang snaps (also known as Throwdowns, snap-its, poppers, pop-its, snappers, whip'n pops, whipper snappers, fun snaps or snap'n pops) are a type of small novelty firework sold as a trick noisemaker.
However, I think the more common word would be, as Jim mentioned, firecracker,
A firecracker (cracker, noise maker, banger, or bunger) is a small explosive device primarily designed to produce a large amount of noise, especially in the form of a loud bang; any visual effect is incidental to this goal.