What is browser session management?

Session management is keeping the state that ties a series of requests together. HTTP is stateless, so a site recognises a returning visitor only through what the visitor carries: cookies, local storage, and often the address the requests arrive from.

For anything behind a login, or any flow with steps, that state is the whole game. Lose it and step three does not know what happened in step two.

What actually makes up a session

• Cookies. The main mechanism. A session cookie issued at login identifies you on every subsequent request.
• Local and session storage. Some applications keep tokens here rather than in cookies, and these are not sent automatically. They have to be preserved by keeping the same browser context alive.
• The IP address. Many sites bind a session to the address that established it, which is why rotating proxies and authenticated flows are incompatible by default.
• A consistent fingerprint. A session whose browser characteristics change mid-flow is a contradiction no real visitor produces.

The third one causes the most confusion, because the symptom looks like blocking. Logging in successfully and being logged out on the next request, a cart emptying between steps, pagination resetting to page one, or a 401 partway through a crawl are usually a rotating address rather than detection.

Isolation between sessions

The other half of the problem is keeping sessions apart. Scraping several accounts, or several regions, from one browser means their cookies mix, and a site can trivially link them.

Browser contexts are the mechanism. Playwright and Puppeteer both support multiple isolated contexts inside one browser process, each with its own cookie jar and storage, which is far cheaper than launching a browser per identity. One browser, many contexts, one identity per context.

Reusing a session rather than re-establishing it

Logging in is expensive: several requests, sometimes a challenge, sometimes a second factor. Doing it before every scraping run wastes that cost and creates a suspicious pattern of repeated logins from the same client.

Saving the cookie jar after a successful login and restoring it on the next run avoids both. Sessions expire, so the pattern is to try the saved state, detect the logged-out case, and re-authenticate only when needed.

Where Zenrows fits

For plain Fetch requests, the session ID parameter pins requests carrying the same ID to one IP address, which is what keeps a sequence of authenticated calls intact without giving up rotation everywhere else.

For flows needing a real browser, Browser Sessions holds a live session you drive with Puppeteer or Playwright, with session TTL configurable from one to fifteen minutes so it lasts as long as the flow rather than being torn down mid-login.