Moving page data to localhost when fetch to 127.0.0.1 hangs

Some third-party pages can't reach a local receiver: fetch and sendBeacon to 127.0.0.1 just hang, and the renderer can freeze until the tool times out. A workaround is to navigate to a page on a site you control or are logged into, with the data base64-encoded in the URL fragment, then POST it to localhost from that origin. Fragments aren't sent to the server, and about 186 KB survived the redirect in Chrome. Clear it afterwards with history.replaceState, and wrap fetches in AbortSignal.timeout so a hang can't block the tool. Never put credentials in the fragment, because it stays in browser history.