Mark Jaquith

When your posts get a lot of comments, performance can be a concern. The generation of the comment HTML and the delivery of all that HTML can slow down your page loads. This plugin has pages load without comments, and then uses a secondary AJAX request to pull down the comments. Navigating through the pages of comments is also handled via AJAX. On my test install with 100 comments per page, the <code>onload</code> event fires 2x faster. The HTML is generated by the server 6x faster. The HTML downloads 3x faster. The uncompressed size of the HTML is reduced by a factor of 17.
Initial development of this plugin was commissioned by Google — many thanks!

AJAX Comment Loading

Loads comments with a secondary AJAX request, including comment paging. Speeds initial loading of the page.

wilcosky

Frontend Loader is a WordPress plugin designed to add a sleek, minimal loading spinner to your website, offering an enhanced user experience reminiscent of native applications. It intelligently detects ajax requests, link clicks, and page loads to activate, excluding WordPress heartbeat actions to avoid unnecessary activations. A settings page provides a way to tell the plugin to ignore certain types of clicks and/or ajax requests based on CSS selectors (Classes or IDs).
This plugin is brought to you by SkyWolf, Billy Wilcosky, and generous donators like you! If this plugin enhances your website, consider supporting development: https://www.buymeacoffee.com/billyw 
Suggested donation is $5.
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Frontend Loader aims to provide an app-like loading experience, enhancing your site’s feel and responsiveness. We appreciate your support and feedback to continually improve this plugin.

Frontend Loader

A minimal loading spinner for WordPress that enhances your site with app-like loading behavior.

AJAX Comment Loading vs Frontend Loader