Smartproxy is a residential proxy provider.
They offer access from over 195 locations spread all over the world. Their pool of 10+ million residential IPs is very convenient for its many users. They even provide residential IPs from eight major cities.
Furthermore, their clients can choose to rotate their IPs every ten minutes, or how they see fit. In case of an issue, they offer customer support whose reaction time is within a 5-minute time frame.
Marketers use Smartproxy, online researchers, data scrapers, and anyone that needs uninterrupted access to websites without any geo-restriction. What makes them so convenient is their massive pool of IPs.