[zinekeller]

Yeah, the name is straight from marketing (implying happy people seeing a fast website). It simply means that clients detect which is the better connection (whether IPv4 or IPv6) rather than naive IPv6-first or IPv4-first. RFC Standards about this: https://datatracker.ietf.org/doc/html/rfc6555 and https://datatracker.ietf.org/doc/html/rfc8305

Unfortunately OkHttp is naively priotising IPv6 regardless if the IPv6 connection is good or not.

[tadfisher]

The latest release now has a Happy Eyeballs implementation.