Shared Proxy

A shared proxy has its exit IP used by several customers simultaneously. Sharing the address spreads the cost, so shared proxies are cheap, but you inherit whatever the other users do. Because reputation attaches to the IP rather than to you, another user's abuse can get the address challenged or blocked before you even arrive. It is the opposite of a dedicated IP, which no one else touches.

When you send a request, it mixes with traffic from every other user of that address. For low-stakes, tolerant targets this is fine and economical. But on strict sites the shared history is a liability: a neighbour's aggressive scraping can raise the address's fraud score, and you feel the consequences. Shared addresses are also poor for whitelisting and stable sessions, since you do not control who else is on them or what reputation they leave behind.

The free s4m public proxy list is inherently shared and best-effort — great for testing and light tasks, continuously re-checked, but with no guarantee about who else is using an address. When you need a clean history and predictable behaviour, an s4m dedicated / personal IP gives you an exclusive address that no one else uses, which you can whitelist and keep in good standing. See the proxy plans to compare.