indicates the application-layer protocol that a client intends to use within the tunnel, or a set of protocols that might be used within the tunnel.
Quick facts
Description
indicates the application-layer protocol that a client intends to use within the tunnel, or a set of protocols that might be used within the tunnel.
Syntax
ALPN: h2
Frequently asked questions
indicates the application-layer protocol that a client intends to use within the tunnel, or a set of protocols that might be used within the tunnel.
It is classified as a request header and can appear in requests or responses depending on context.
Sources & standards
Updated 2026-09-13
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