Sticky session
A setting that keeps the same exit address for a fixed period, so a multi-step flow appears to come from one user.
A sticky session holds one exit address for a defined duration instead of rotating. Typical windows run from one minute to roughly thirty, depending on the provider.
#Why it exists
Many tasks are not a single request. Logging in, adding to a basket, paging through results, or completing a form all involve several requests that a server expects to originate from one client. If the address changes halfway through, the session looks implausible and may be discarded or challenged.
#How it is usually requested
Most providers accept a session identifier inside the proxy username, for example a field such as session-abc123. Requests carrying the same identifier are routed through the same address until the window expires. The exact syntax differs by provider.
#What it does not guarantee
Stickiness is best-effort. If the underlying address leaves the pool — a residential peer disconnects, for example — the session ends early and you receive a different address. Code that assumes a stable address for the full window will eventually be surprised, so detect the change rather than assume it cannot happen.
#What sticky does and does not promise
| Promise | Holds? |
|---|---|
| Requests in the session prefer the same exit | Yes, while that exit is reachable |
| The address never changes | No. A consumer device can leave at any moment |
| The session lasts as long as you want | No. Providers cap the duration |
| The address stays in the chosen country | Usually, but confirm after any replacement |
Because the second row is false, code that depends on a stable address must detect the change rather than assume it cannot happen. Check the address at the start of the session, and again after any unexpected authentication failure.
#Building for the replacement
A session that loses its exit usually presents as a sudden logout, an empty basket, or a redirect to a sign-in page. Treat those as a possible address change, not only as an application error. The recovery is to open a new session deliberately and restart the flow, rather than to retry the failed request on an address the site no longer associates with your state.
The rotation guide covers where each model belongs.