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.

TylerShaw

What’s It Do?
This plugin adds a box to your pages and posts allowing for page-specific or post-specific CSS stylesheets.
Why Use It?
After developing quite a few WordPress websites, it seems to me that the style.css file gets bloated. If you add a style used on only one page, and then later that page is deleted, you’re visitors now have to download those styles that aren’t even used. It’s wasteful, but maintaining a clean style.css file requires an active effort. This plugin solves that by attaching the these styles to the page or post, allowing them to be updated just like the content is and deleted with the page.
It keeps your style.css file clean and reduces unused style clutter.
What About Efficiency?
There shouldn’t be an issue with overhead from the plugin. Admin code is only executed in the admin panel and front end code is executed on the front end. If you’re website has a large amount of page-specific styles within it that can be migrated into the plugin, it can boost performance by reducing the download size of your style.css file.
Roadmap
This plugin will receive ongoing maintenance as WordPress evolves. No major features are planned, but I am entirely open to feature requests!
Feel free to suggest any feature you desire, or check out the code or contribute on <a href="https://github.com/tyler-shaw/page-specific-stylesheets" rel="nofollow ugc">GitHub</a>, where the project is hosted.
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<li>Additional plugin options.</li>
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If you have a feature idea, suggest it.
Notes
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<li>Style data and options are not deleted by default on uninstall. You must check the options on the plugin settings page to enable the deletion of this data.</li>
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Page Specific Stylesheets

Adds a box allowing for the addition of page-specifc and post-specific CSS stylesheets. Reduces the need to edit and clutter up the style.css file.

WP Add Custom CSS vs Page Specific Stylesheets