This test will read the HTTP Header of your URL and tell you whether keep-alive connections are enabled by detecting the keep-alive configurations listed in the header response.
It will work irregardless of the type of server (ie. Apache, Microsoft/IIS, NGINX), OS (Linux, Windows) or CMS (ie. Wordpress, Joomla, Drupal) you're running as long as the HTTP header will return keep-alive information.
Connection: keep-alive means keep-alive is enabled.
Connection: close means keep-alive is not enabled.
Connection: none detected means the test wasn't able to retrieve the necessary information from the response headers of your URL to detect whether keep-alive was enabled or not.
Take a look at this article to learn how to enable keep-alive.
Enabling keep-alive makes it possible to use just one TCP/IP connection to retrieve multiple web files (the files your web pages load) at once instead of having to create a connection for every single file. This speeds up the process of retrieving your web files since using one persistent TCP/IP connection instead of using multiple connections will result in faster page load times. Read more about this here.
Analyze your CSS to make improvements to the CSS Delivery.
Minimize CSS scripts and files for page speed.
Minify your JS files and scripts to maximize performance.
Check whether your web pages have Gzip compression enabled.
Tests your image delivery so you can improve it.
Reduce your PNG image filesize while keeping quality.
Play with the quality and size of JPEGs to save disk space.
Place multiple images in one image to make fewer requests.
Check how and whether your website files are cached.
Test your web pages for broken links and requests.
How many HTTP requests do your web pages produce?
Encode JPEG and other files into a Base64 string.
Check whether your website has keep-alive settings as enabled.
Remove line breaks from your scripts to save disk space.
Check the HTTP server header of your site.