<a href="http://pjdietz.com/wordpress-plugins/custom-css-js/" rel="nofollow ugc">Custom CSS and JS</a> allows you to add stylesheets and JavaScripts to any individual post by adding custom fields. Both CSS and scripts can be either internal or external. Since this is a plugin, the custom CSS and JavaScript are available to any theme used to display the post, as long as the themes call “wp_head”.
<h3>Using the Plugin</h3>
To use the plugin, add any combination of the following custom fields to your post.
custom_css 
Add an external stylesheet by adding a custom field with the name custom_css. The value of the field should be the path to your css file.
cusrom_css_code 
Add an internal stylesheet by adding a custom field with the name custom_css_code. Include your CSS code as the value. (Do not include the style tags.)
custom_js 
Add an external JavaScript by adding a custom field with the name custom_js. The value of the field should be the path to your script.
custom_js_code 
Add an internal JavaScript by adding a custom field with the name custom_js_code. Include your JavaScript code as the value. (Do not include the script tags.)
<h3>Custom Fields Order</h3>
<ol>
<li>The external styles and scripts are included before the internal ones.</li>
<li>If you include multiple entries for a given field, the entries will be included in order.</li>
</ol>
<h3>Okay, but what if I don’t like those tags?</h3>
Just edit custom-css-js.php and change the constants defined near the top of the file.
<h3>Note</h3>
This plugin only works with individual posts and pages. It does not work for list pages (e.g., the index page, search results).

Custom CSS and JS

Custom CSS and JavaScript allows you to add custom internal and external CSS and JavaScripts to individual posts.

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.

Custom CSS and JS vs WP Add Custom CSS