Include "beacon" ResourceTiming entry. The current Resource Timing spec expects beacon resource loads: https://w3c.github.io/resource-timing/ Spec text: > On getting, the initiatorType attribute must return one of the following DOMString values: > ... > "beacon", if the request is the result of processing the sendBeacon method [Beacon]; Test: 1. Load https://tests.caniuse.com/?feat=beacon 2. Wait a while so beacons could be fulfilled 3. js> performance.getEntriesByType("resource") => No "beacon" entries Notes: - No other browser I tested included beacon loads in Resource Timing - Note adding entries to the performance timeline exposes when the beacon was sent / response received. I don't think thats a bad thing.
I filed https://github.com/w3c/resource-timing/issues/377 to track this.