Server Push is Supported on LiteSpeed Web Server

Server Push is a method of information delivery whereby a server pushes a resource directly to the client without first receiving a request to do so. By doing this, the server can attempt to anticipate client requests and pre-push them into the client’s cache in an effort to avoid the usual request-response round trip delay.

1. LiteSpeed Enterprise 5.2+
2. HTTPS enabled
3. HTTP/2 supported by the browser

NOTE: This article focuses on HTTP/2 server push, but server push may also be used with HTTP/3, assuming the browser supports it.

We are going to introduce how to verify Server Push with WordPress+LSCache, and then with Cloudflare.

If you would like to try server push and file making from scratch, please see this guide to learn how.

1. Server Cache Setup
2. WordPress Installation
3. LSCache for WordPress

There are two easy ways to verify your browser has HTTP/2 support:

1. Check your browser version against the table at this link. (Use this link for HTTP/3.)
   
2. Visit the Akamai online tool and let it auto-detect your browser's support.
   

1. From the WordPress Dashboard, navigate to LiteSpeed Cache > Page Optimization > CSS Settings and set CSS HTTP/2 Push to ON
2. Switch to the JS Settings tab and set JS HTTP/2 Push to ON

We are going to use the Chrome developer tool as our verification tool.

• If you only enabled CSS HTTP/2 Push, the response header will look like this:
  
  
• If you enabled both CSS HTTP/2 Push and JS HTTP/2 Push, the response header will look like this:
  
  

CSS and JS files will show as Push / Other:

Next we'll try it with Cloudflare. Cloudflare supports HTTP/2 Server Push with the link header field on all plan levels. Cloudflare will look for the link header field, in response headers from the origin server and extract URI-references with parameters rel=preload. These URI will be pushed to the client.

Follow this LiteSpeed blog to Set up CDN from LSCache

• If you only enabled CSS HTTP/2 Push, the response header will look like this:
  
  
• If you enabled both CSS HTTP/2 Push and JS HTTP/2 Push, the response header will look like this:
  
  

1. Point your browser to chrome://net-internals/#http2
2. Refresh your test site
3. You will see HTTP/2 sessions
   
4. Click the hyperlink of your test site's ID
5. The Events tab will open, and you will see HTTP2_SESSION. Enable the checkbox.
   
6. Check the HTTP2_SESSION_RECV_HEADERS → link section, which will look like this:
   

   rel=preload; as=style,</wordpress/wp-content/plugins/litespeed-cache/css/litespeed.css>; rel=preload; as=style,</wordpress/wp-includes/js/admin-bar.min.js>;

We welcome your feedback on our forum.

If you want to disable the ls_smartpush cookie for a particular domain, you can use the SmartPush no-cookie directive in .htaccess starting from LSWS v5.4.2.

<IfModule LiteSpeed>
  SmartPush no-cookie
</IfModule>

After you make changes to .htaccess, you will need to restart your browser to avoid getting a cached version. After that, you should see something like the following: