Privacy
The device remembers even if you did not save anything
Logged-in sessions, autofilled emails and cached images persist on a borrowed or family device after you have closed the tab.
Guides on Privacy: Who could see it, how, and what each path costs to close, Soft delete, backups, caches and logs, Sometimes, and the policy clause that says so is easy to miss
On a shared device, closing the tab does not log you out: your signed-in session, autofilled email and cached images stay behind for whoever opens the same browser profile next.
What a shared device keeps
A logged-in session on most sites persists after the tab closes, sometimes for weeks, because "stay signed in" is the default rather than the exception. Whoever opens the same browser profile next can land straight back on your account without a password, which is convenient for you and identical in effect for anyone else using the same profile. Autofill remembers form fields per browser profile, not per person, so an email typed once during a rating session can surface as a suggestion the next time anyone on that device starts typing an address that begins the same way. The cached thumbnail and result page behave exactly as on a personal device - they sit in local storage until cleared - except here "cleared by someone else" is not a safe assumption.
What actually helps
A private or incognito window avoids most of this on a shared device, because the alternative is a session and cache that outlive your use of the machine entirely. Google's Chrome help page states that after an Incognito session ends, "Chrome doesn't retain site data or a record of the sites you visited," though downloaded files and any bookmarks you save do stay on the device. Signing out explicitly, rather than just closing the tab, is worth doing on anything that is not your own device, since staying signed in is the setting working as intended rather than a bug. What a browser leaves in cache and history more generally applies here too, compounded by the fact that someone else has ordinary access to look. A lock-screen notification preview is the other channel that does not care whose device it is, and is worth checking alongside this one.
Family accounts add another layer
Some services encourage a single account across a household - shared payment, shared history, one login everyone knows - which is a convenience feature for streaming and shopping that becomes a liability for anything you did not mean to be shared. If a rating result lands in a shared account's history rather than a personal one, "signing out on this device" does nothing, because the record was never device-specific to begin with; it is account-specific, and every device signed into that account can see it. Checking whether an account is genuinely personal, rather than a household default nobody set up deliberately, is worth doing once rather than assuming.
Where it connects
Rate Cock uses ordinary session cookies like most web tools, which behave exactly as described above on a device you do not control alone. The same logic applies to a measurement session kept for later comparison, which Measure My Cock's data page covers for its own use case. A commissioned human review tied to an account carries the identical shared-device exposure, something Rate Penis's judge coverage touches on from the review side. Comparing how different rating tools handle session persistence on a shared machine is a subject Penis Rater's tools coverage is better positioned to survey than a single mechanism piece here.