What is HTTP/2 fingerprinting?

After the TLS handshake, an HTTP/2 client sends a set of low-level parameters: SETTINGS frame values, initial window sizes, header-table sizes, and the order and priority of frames and pseudo-headers. Different client stacks produce different, stable patterns — a signature the server reads at the connection level.

Like TLS (JA3/JA4), this sits below JavaScript's reach, so a browser that claims one identity in its headers but emits an HTTP/2 signature from a different stack is incoherent.

Keeping the HTTP/2 layer consistent with the claimed browser is a network-stack concern; because Clearcote is Chromium-core, its HTTP/2 behavior follows real Chrome. See how detection works.