Enable HTTP/2 on Apache Tomcat 9 and 10 with TLS and ALPN
Configure Tomcat to negotiate HTTP/2 over HTTPS using the Http2Protocol connector, then verify ALPN negotiation and plan fallback for older clients.
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tomcatDiagnosing HTTP/2 Enablement Issues in Tomcat 9+ with the NIO2 Connector
When Tomcat reports “Failed to accept HTTP/2 connection: ALPN not available” or clients cannot upgrade, this guide walks through common causes, checks, and fixes to get HTTP/2 working on Tomcat 9+.