Sandesh

HTTP/2 is the new generation HTTP protocol that provide tremendous powers the web. HTTP/2 is future of web. The most powerful feature of HTTP/2 is server push. Most of popular hosting providers supports to Server Push. Server Push provides significant performance gains if used judiciously.
Check <a href="https://http2.akamai.com/demo" rel="nofollow ugc">HTTP/2 Demo Here</a>.
Server Push allows the server to “bundle” assets that the client didn’t ask for.It send resources to the browser before it even realizes it needs them. This avoids the usual HTTP request/response cycle.
This plugin enabled WordPress to send a <code>Link:<...> rel="prefetch"</code> header to every enqueued script and style page. Is doesn’t support who output their scripts directly into the page itself. This plugin doesn’t affect any visual part of site.
Read more about <a href="https://blog.cloudflare.com/announcing-support-for-http-2-server-push-2/" rel="nofollow ugc">server push here</a>
Note : It requires a web server that supports HTTP/2.
<h3>WordPress 4.6 and above</h3>
WordPress 4.6 introduced support for <a href="https://make.wordpress.org/core/2016/07/06/resource-hints-in-4-6/" rel="nofollow ugc">resource hints</a>. 
This plugin defers to WordPress 4.6 and theme/plugin developers to responsibly prefetch the right assets.
I’ve added a filter To restore the old behavior of resource hints on WordPress 4.6 and above. Use following filter in your functions.php file or in a custom plugin:
<pre><code>`add_filter('sjh_http2_resource_hints', '__return_true');```
</code></pre>

SJ HTTP/2 Server Push Optimization

SJ HTTP/2 Server Push Optimization for JavaScript and CSS resources enqueued in the page.

shawfactor

Server Push provides significant performance gains if used judiciously. However other WordPress plugins that handle server push can actually slow your site as they push files indiscrimentally.
Most push all files enqueued by wordpress to the broswer and use output buffering to achieve this.
However this plugin does it properly by only pushing the the assets that the browser requires for the initial user interaction. Namely the scripts and css in the head of the document.
Note : It requires a web server that supports HTTP/2.

LH HTTP/2 Server Push

Does HTTP/2 Server Push for JavaScript and CSS resources properly.

SJ HTTP/2 Server Push Optimization vs LH HTTP/2 Server Push