If a provider charges no fee, is the transfer free?

Not necessarily, because a provider with no visible fee can still earn through the exchange rate margin. If the rate offered is weaker than the mid-market rate, that gap is a real cost, even though it never appears as a line on your receipt. A modest fee with a good rate can beat no fee with a weak rate, and the reverse can also be true. The reliable test is the total amount the recipient receives for the same send amount at the same moment, after all disclosed charges.¹