Even though fornecido por has been used in place of powered by already I’d like to present some alternatives for you consideration. Namely:
Here are my reasons. Suppose you have webpage X which uses some functionality Z supplied by firm Z, but functionality Z does not do all the work, it only helps webpage X to work seamlessly; or we might say functionality Z enables webpage X. So any of the alternatives above sort of conveys that idea, and has a more upbeat feel to it than fornecido por. Habilitar, tornar hábil ou apto a, prover (outrem) do preciso (para um fim) corresponds more closely to enable. It might take some getting used to, because it also has a legal meaning which is not relevant here. Otherwise it’s probably my favourite, followed by assistido por.
The literal translation of powered by is of course movido por, motorizado por. As used in the present context I suppose all powered by means is precisely enabled by, made to work by. which is not far from the phrases I suggested.