A proxy pool is the full inventory of IP addresses a proxy provider maintains for rotation and customer assignment. Pool size — often measured in millions of IPs for residential providers — determines how long a rotation strategy can run before repeating an IP against a given target.
Not all pool IPs are equal: freshness (how recently tested), geographic distribution, and subnet diversity all affect scraping success rates. Premium proxy providers maintain "clean" pools by continuously testing IPs against common targets and retiring burned ones. Pool quality matters more than raw pool size for demanding scraping use cases.