Project to reproduce HTTP 431 when header is too large See quarkusio/quarkus#33692 Build and run mvn clean package && java -jar target/maven-simplest-*.jar Example request curl -k 'https://localhost:8443/' \ -H "x-foo: $(printf -- 'A%.0s' {1..9872})" \ -o /dev/null -s -w '> bytes sent: %{size_request}' \ -vv 2>&1 |grep -E '(<|>)'