Rotating: a different address every request
Right whenever requests are independent of each other. Crawling a large number of pages is the classic case, per IP rate limits stop applying to you as a whole, because no single address carries much of the traffic.
Sticky: one address, held
Required for anything with state. Logins, carts, multi step forms and account management all break when the address changes underneath them, and the breakage is often silent, a session that quietly stops working rather than an error.
Rotating during a session is a red flag, not a defence
A logged in account whose IP changes every request looks precisely like a stolen account being used from a botnet. This is the single most common way people get flagged while believing they are being careful.
Session length is configurable
Sticky windows are set when you generate the lines, from short holds up to long ones depending on the pool. Pick a window that comfortably covers your longest single flow.
What to buy
Rotating for crawling. Sticky for anything that logs in, holds a cart, or spans more than one request.
Common questions
What is the actual difference?
Rotating gives you a different address on each request. Sticky holds one address for a set period. Nothing else changes, it is the same pool and the same addresses either way, and the choice is only about whether consecutive requests should look like one visitor or many.
Which one should I use?
Sticky whenever the requests depend on each other, such as anything with a login, a cart, or a multi step form, because those break the moment the address changes underneath them. Rotating for independent requests, because spreading work across many addresses is what keeps any single one from carrying an unnatural pattern.
How long can sticky sessions last?
It depends on the pool. Residential holds up to six hours here, mobile up to one hundred and twenty minutes, and ISP can be pinned to a static address for the whole term. IPv6 does not offer sticky at all and always rotates.