Esri has a free address auto-complete API, and unlike Google who suggests addresses that aren't legal, USPS deliverable addresses, you nearly always get real, v

Esri has a free address auto-complete API, and unlike Google who suggests addresses that aren't legal, USPS deliverable addresses, you nearly always get real, valid addresses from Esri since they are pulling USPS's dataset (who is the only org that is legally required to getsl notified when a city or county renames a road, renumbers a block of buildings, etc).