How to Enable HTTP/2 on Your Site
HTTP/2 is a binary multiplexed protocol that speeds up 10-30% of sites with no code changes. Requirements: HTTPS (mandatory), nginx ≥ 1.9.5, Apache ≥ 2.4.17 with mod_http2, OpenSSL ≥ 1.0.2 with ALPN. Enable with one config line. For Cloudflare/CDN it is already on.
Below: step-by-step, working examples, common pitfalls, FAQ.
Step-by-Step Setup
- Check versions:
nginx -V(≥ 1.9.5),openssl version(≥ 1.0.2 for ALPN) - In nginx replace
listen 443 ssl;withlisten 443 ssl http2; - Apache:
a2enmod http2+ addProtocols h2 http/1.1to vhost - Syntax check:
nginx -t/apachectl configtest - Reload:
systemctl reload nginx/systemctl reload apache2 - Verify via Enterno SSL/TLS Checker — ALPN will show h2
- Or in shell:
curl -I --http2 https://example.com
Working Examples
| Scenario | Config / Record |
|---|---|
| nginx minimal | server { listen 443 ssl http2; server_name example.com; ssl_certificate /path/fullchain.pem; ssl_certificate_key /path/privkey.pem; } |
| Apache 2.4.17+ | Protocols h2 http/1.1 (inside <VirtualHost *:443>) |
| Cloudflare | Dashboard → Network → HTTP/2 = ON (default) |
| HTTP/2 Push (deprecated) | Chrome 106+ removed Server Push. Use <code>103 Early Hints</code> instead. |
Common Pitfalls
- HTTP/2 works ONLY over HTTPS — browsers do not support HTTP/2 cleartext
- OpenSSL older than 1.0.2 (CentOS 6, Ubuntu 14.04) lacks ALPN → HTTP/2 unavailable
- Apache prefork MPM is incompatible with mod_http2 — switch to event MPM
- HTTP/1.1 browser connection pooling can be faster for some workloads — always measure
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How-to
Frequently Asked Questions
Is HTTP/2 always faster than HTTP/1.1?
No. On sites with a single large JS bundle the difference is tiny. On sites with many resources (CSS + many images + fonts) HTTP/2 yields a 10-30% gain from multiplexing.
Do I need to change code?
No. HTTP/2 is a transport change, the API is identical. Just drop legacy optimisations (domain sharding, inline critical CSS blocks) — they hurt HTTP/2.
Is HTTP/3 ready?
Yes, with nginx 1.25 (March 2023) stable. Or via Cloudflare automatically. Biggest gains on mobile networks. See our <a href="/en/s/research-http3-quic-adoption-2026">HTTP/3 adoption research</a>.
How do I verify HTTP/2 actually works?
<a href="/en/ssl">Enterno SSL Checker</a> or <code>curl -I --http2 https://site.com</code> — the response must include <code>HTTP/2 200</code>.