Happy Eyeballs Version 3
Combined Test

Our specialized web server introduces targeted, artificial delays during the transport-layer protocol handshake (based on the TLS SNI). This capability allows us to selectively delay either the TLS/TCP or the QUIC handshake.

We utilize a similar SNI-based approach to introduce IP-version-specific delays during the initial handshake. Alternatively, you can configure the test to apply continuous delays to every IPv6 packet. In this per-packet scenario, each IP delay maps to a dedicated IP address configured with tc netem.

To signal HTTP/3 (QUIC) availability, our DNS nameserver responds with HTTPS resource records for all test domains. The specific contents of these HTTPS records can be customized in the settings.

Note: For the test to function properly, your browser must query and respect these records. You can verify your browser's compatibility using our HTTP/3 availability test .

During the test, the browser establishes connections across all permutations of transport-layer and IP-level delays. This allows you to observe exactly if and how the browser handles the Happy Eyeballs version 3 race across both transport protocols and IP versions.

We randomize domains to try to prevent caching effects on the browser's side as much as possible. Furthermore, we aggressively close connections on the server side after every request, forcing the browser to perform a fresh handshake for each new test.