HTTP/2 Disabled by Default in Nginx 1.19 – Need Explicit http2 Flag

Problem

Locally the server runs Nginx 1.15, where a simple listen 443 ssl directive implicitly enables HTTP/2. The same configuration is deployed to production, which uses Nginx 1.19. In this newer version HTTP/2 is no longer enabled by default, so clients that expect HTTP/2 fail to negotiate the protocol, causing degraded performance and compatibility issues.

Goal

Guarantee that HTTP/2 support is consistently enabled across all environments, regardless of the Nginx version or build.

Constraints & Uncertainty

• The production build may include or exclude the ngx_http_v2_module module.
• Custom builds or patched binaries could retain the legacy default behavior.
• Version detection and configuration drift between local and production are not automatically verified.

Unresolved Questions

1. What automated checks can confirm whether a given Nginx installation will enable HTTP/2 without the http2 flag?
2. What is the most reliable configuration pattern to enforce HTTP/2 across all supported Nginx releases?
3. How do module availability and custom build options influence HTTP/2 support in practice?