WP-Optimize
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Speed Up
This plugin load the stylesheets asynchronously and improve page load times.
The facts
- Rating
- 5★ from 8
- Active installs
- 500+
- Price
- Free
- Last updated
- 26 Jul 2026
- Added
- Dec 2016
- Requires WP
- 6.0
- Tested up to
- WP 7.0.4
- Requires PHP
- 7.0
- Downloads
- 61,023
Our analysis
AI-assistedSpeed Up – Optimize CSS Delivery is a WordPress plugin designed to enhance page load times by loading stylesheets asynchronously. It aims to improve performance by allowing you to configure which stylesheets load synchronously and which load asynchronously through a filter in your theme's functions.php file.
However, the plugin is no longer recommended due to its potential to cause layout shifts, which can negatively impact Core Web Vitals. It is best suited for users who have a good understanding of CSS delivery and want to experiment with stylesheet loading configurations.
Best for: This plugin is suitable for advanced users who want to manage CSS loading on their WordPress site.
What it does well
- ✓Loads stylesheets asynchronously to improve page load times
- ✓Allows configuration of synchronous and asynchronous stylesheet loading
- ✓Lightweight plugin at 5 Kb
Where it falls short
- •No longer recommended for optimal performance
- •May cause layout shifts if not configured correctly
- •Requires correct CSS handling by other plugins and themes
Verdict
While it offers specific functionality for CSS delivery, its lack of current recommendations and potential issues with layout shifts may limit its effectiveness.
From the developer
nigro.simone's own description of Speed Up, lightly tidied.
This plugin is no longer recommended. Deferring every stylesheet makes the page paint before its own layout arrives. That flash of unstyled content is measured as Cumulative Layout Shift — one of the Core Web Vitals this plugin is meant to improve.
The current advice is to inline the CSS needed for the top of the page and defer only the rest, which is more than rewriting a link tag can do.
If you have not configured the exclusion filter for your main stylesheets, deactivating this plugin will most likely improve your scores rather than worsen them.
This small plugin (5 Kb) loads the stylesheets asynchronously and improve page load times.
The recommended use of this plugin is to load your vital stylesheets synchronously and non-vital CSS files asynchronously.
Non-vital CSS-files can be for example: fonts, icons, before the fold template-specific CSS, etc.
You can choose which files to load synchronously with a filter in your function.php, eg.:
// exclude main and child stylesheets from delivery optimization
function exclude_from_delivery_optimization($handle){
return in_array($handle, array('main-stylesheet', 'child-stylesheet'));
}
add_filter('speed-up-optimize-css-delivery', 'exclude_from_delivery_optimization');
Note: this only works if your other plugins and theme add the CSS correctly.
Tagged as
purpose
Performance & Speed
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