Why Cached Browser Pages Can Hide a Failed Proxy

A previously visited page can render after its proxy stops working. The browser may be displaying cached content, including an old exit address on an IP-check page.

1. Open the browser's Network panel before making a new request. In Chrome DevTools, disable the browser cache while DevTools remains open.
2. Request a controlled endpoint whose response is suitable for a fresh check.
3. Inspect what completed the request: network response, memory or disk cache, service worker, or failure. Record a network failure even if cached document content still renders.

Only an actual request on the intended route is a proxy transaction to evaluate. A browser control's navigation-completed event reports document loading, and frames can produce several completion events; it does not answer the route-health question.

For an automated list checker, candidates from the free proxy list still need a dedicated HTTP request with an explicit route and timeout rather than cycling global browser settings. Record the request outcome, including a destination rejection that may arrive over an otherwise working proxy.