Best/worst. I worked at an e-learning company that, thanks to ancient e-learning standards, really tried hard to figure out when a user is leaving a web-page to handle session exits gracefully.

sendBeacon was dead on arrival, for that purpose at least; iirc it's blocked by most ad blockers. (Or was, who knows with Manifest v3.)

Similarly we're unlikely to see sendBeacon truly replace tracking redirects, unfortunately. This isn't an area where tech firms are happy to see fine user controls.

Wheb I implemented an in-house analytics system, I had to revert to using a normal fetch request, as by default any usage of the beacon API was blocked. I don't think it really makes a difference for big providers with well-known blacklisted domains, but for custom implementations, it does