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Cookies Differ Between Replay and Recording

If you inspect cookies in Headers View and notice that the replay values don't match the recording values, your first reaction may be that something's broken. It's not. Cookies differing between replay and recording is normal, expected, and almost always correct behavior.

Why This Happens

Load Tester simulates a real browser, not a playback-only tool. When the server sends new cookies during replay (fresh session IDs, updated timestamps, rotating CSRF tokens), Load Tester accepts them and uses them in subsequent requests, exactly like a real browser would. Servers generate fresh session IDs for each login. CSRF tokens change on every request. Timestamps update dynamically. If Load Tester replayed the exact recorded cookies verbatim, most applications would reject them as expired or invalid.

So when you see different cookie values during replay, that's the test case behaving correctly. The recorded cookies were captured at recording time and have nothing to do with the live session.

Only worry about cookie differences if:

  • Replay fails with authentication errors (401 / 403)
  • The application expects a specific cookie value that Load Tester isn't providing

If replay succeeds (green transactions, correct content), different cookie values are fine. Stop worrying about them.

For unusual scenarios where you need to override cookie values or extract specific cookie values for use elsewhere:

For 401 / 403 failures involving session cookies, the systematic debugging path is Debugging 401 and Debugging 403.