Long: no-npn Tags: Versions HTTP/2 Protocols: HTTPS Added: 7.36.0 Mutexed: See-also: no-alpn http2 Requires: TLS Help: Disable the NPN TLS extension --- Disable the NPN TLS extension. NPN is enabled by default if libcurl was built with an SSL library that supports NPN. NPN is used by a libcurl that supports HTTP/2 to negotiate HTTP/2 support with the server during https sessions.