Full definition
An ISP proxy is the hybrid solution: the physical server lives in a datacenter (so you get fast speeds and stable connections), but the IP address is registered to a real consumer ISP via a peering agreement. To anti-bot systems, the IP looks residential. To your code, it behaves like a datacenter IP — same IP for every request unless you rotate manually.
This is the right pick when you need a session that lasts hours or days (e.g., maintaining a logged-in account), need predictable performance for benchmarks, or want to whitelist a specific IP at a destination. The downside is volume: each ISP IP costs $1.50–$6 per IP per month, so building a pool is expensive compared to per-GB residential pricing.
Top providers: Bright Data, Rayobyte, IPRoyal, NetNut. Often marketed as "static residential" — same thing, different name.