dwieeb

With this plugin, you will be able to include certain CSS or JS files in only selected posts, pages, or other post types, instead of including them everywhere. You can also edit inline CSS & JS and include CSS & JS files from anywhere on specific posts and pages.
It places meta boxes in the WordPress post editor so it’s easy to select which files you want to include with the post you’re currently editing. This plugin works well for all websites, large and small, and it works well with WordPress multi-site (WordPress MU). Tested up to 3.1 beta 2.
See this plugin’s <a href="http://www.danielimhoff.com/wordpress-plugins/specific-files/" rel="nofollow ugc">page</a> on my website for information/comments/questions. I am open to the idea of suggestions and patches to this plugin! If you enjoyed this plugin, please <a href="http://www.danielimhoff.com/donations/" rel="nofollow ugc">donate</a> or <a href="http://www.danielimhoff.com/donations/" rel="nofollow ugc">say thanks</a>.
Todo:
<ul>
<li>Add a “remove references” button on the options page so people can remove file references without having to delete the file.</li>
</ul>

Specific Files

This plugin allows you to include CSS or JS files in specific posts and pages.

Daniele De Santis

WP Add Custom CSS allows you to add custom CSS to the whole website and to individual posts, pages and custom post types (such as Woocommerce products). 
The CSS rules applied to the whole website will override the default stylesheets of your theme and plugins, while the CSS rules applied to specific pages, posts or custom post types will override the main stylesheet too.
The plugin works with the most popular builders, such as Elementor, Gutenberg and the Classic Editor.
You can edit the main stylesheet from the the “Add custom CSS” settings page. 
The plugin also creates a new “Custom CSS” box in the editing area to add custom CSS to specific posts, pages and custom post types.
Select the preferred CSS output method from the plugin’s settings page to ensure seamless integration with caching and minification plugins or to improve above-the-fold rendering performance.

WP Add Custom CSS


Says it has not been tested against recent versions, but it works great still. Simple and elegant solution. Sep 13 2024


Still works great

Add custom css to the whole website and to specific posts and pages.

Specific Files vs WP Add Custom CSS