Enabling HTTP2 and HTTP3 on Nginx

HTTP/2 Benefits

• Multiplexing — multiple requests over a single connection
• Header compression — reduces overhead
• Server push — proactively send resources

Enable HTTP/2

HTTP/2 requires HTTPS. Simply add http2 to your listen directive:

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name example.com;

    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    # SSL optimization
    ssl_session_cache shared:SSL:10m;
    ssl_session_timeout 1d;
    ssl_protocols TLSv1.2 TLSv1.3;
}

Enable HTTP/3 (QUIC)

HTTP/3 uses QUIC (UDP-based). Requires Nginx 1.25+ or OpenResty:

server {
    listen 443 ssl;
    listen 443 quic reuseport;
    http2 on;

    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    # Advertise HTTP/3 support
    add_header Alt-Svc 'h3=":443"; ma=86400';
}

Ensure UDP port 443 is open in your firewall:

sudo ufw allow 443/udp

Verify

# Check HTTP/2
curl -I --http2 https://example.com

# Check via browser DevTools → Network → Protocol column