How to Enable HTTP/2 on Your Server

What the HTTP/2 check tests

SiteCurl connects to your server over TLS and checks which HTTP protocol version is negotiated via ALPN (Application-Layer Protocol Negotiation). If the server responds with h2, it supports HTTP/2. If it responds with http/1.1, the server is using the older protocol.

HTTP/2 detection requires HTTPS. Sites served over plain HTTP skip this check.

Why it matters

HTTP/1.1 opens a separate connection for each file the browser needs (images, CSS, JavaScript). With a limit of 6 connections per domain, files queue up and wait. HTTP/2 multiplexes all requests over a single connection, so the browser can download everything at once.

For pages with many assets, HTTP/2 can cut load time by 15-50%. It also supports header compression and server push, further reducing overhead.

How to fix it

Nginx

Nginx supports HTTP/2 out of the box. Add http2 to your listen directive:

server {
    listen 443 ssl http2;
    # ... rest of your config
}

Requires Nginx 1.9.5+ and OpenSSL 1.0.2+.

Apache

Enable the mod_http2 module and add the protocol directive:

Protocols h2 http/1.1

# In your virtual host
<VirtualHost *:443>
    Protocols h2 http/1.1
    # ... rest of your config
</VirtualHost>

Requires Apache 2.4.17+.

CDN

Most CDNs (Cloudflare, Fastly, AWS CloudFront) enable HTTP/2 by default. Check your CDN dashboard to confirm it is turned on. If your origin server does not support HTTP/2 but your CDN does, visitors still get the benefit.

How to verify the fix

Run a SiteCurl scan and check the speed section for the HTTP/2 finding. You can also test from the command line:

curl -sI --http2 https://yoursite.com | head -1

The response should start with HTTP/2.

Related checks

HTTP/2 works best when combined with compression and cache headers. Enabling all three gives the biggest speed improvement.

Start a free trial to check your HTTP/2 support.