c: Copyright (C) 1998 - 2022, Daniel Stenberg, , et al. SPDX-License-Identifier: curl 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 Category: tls http Example: --no-npn $URL --- In curl 7.86.0 and later, curl never uses NPN. 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.