HTTP/2: removed support for NPN. NPN was replaced with ALPN, published as RFC 7301 in July 2014. It used to negotiate SPDY (and, in transition, HTTP/2). NPN supported appeared in OpenSSL 1.0.1. It does not work with TLSv1.3 [1]. ALPN is supported since OpenSSL 1.0.2. The NPN support was dropped in Firefox 53 [2] and Chrome 51 [3]. [1] https://github.com/openssl/openssl/issues/3665. [2] https://bugzilla.mozilla.org/show_bug.cgi?id=1248198 [3] https://www.chromestatus.com/feature/5767920709795840