Ephemeral third-party storage clearing test

What this tests

This page tests whether state written by a third-party iframe is cleared after the embedding first-party site is closed, navigated away from, or after a full browser restart.

The top-level page is the first-party site. The iframe is the third-party site. The iframe writes unique values into storage APIs and cacheable resources, then this page checks whether those values can still be read.

Expected behavior

• Same-session phase: values should be present. This confirms the test can write and read third-party state during the active first-party session.
• After-close phase: values should be absent or changed. If the same value is still present, third-party state survived after the first-party site went away.
• After-restart phase: values should be absent or changed. If the same value is still present after restarting the browser, the third-party state survived across browser sessions.

Before running the after-close test, close any other tabs open to this first-party origin. If another first-party tab remains open, the storage partition may legitimately remain alive.