Blocks CSS allows you add custom CSS to your Blocks straight from the Block Editor (Gutenberg).
As of April 2026, Blocks CSS: CSS Editor for Gutenberg Blocks is a WordPress css plugin with 5.0K+ active installations and a 4.9/5 rating from 25 reviews. It has been downloaded 196K+ times in total. Requires WordPress 6.2+ and PHP 5.4+. Available on WordPress.org since 2019. Actively maintained — updated within the last month. Downloads are down 36% this week. Top alternative: WPCode – Insert Headers and Footers +….
Blocks CSS allows you add custom CSS to your Blocks straight from the Block Editor (Gutenberg).
It adds a syntax-highlighted CSS Editor where you can add additional CSS to your Gutenberg Blocks to style them the way you want.
All the code and sources for this plugin are publicly available as part of https://github.com/Codeinwp/otter-blocks.
Works like a charm on any of my recent WP projects.
[EDIT]
I need to change my review.
On some setups, I get two CSS editors shown in the “Custom CSS” attribute panel, and only contents of the second instance are getting saved.
Problem:
Two CodeMirror editors are displayed in the Custom CSS panel of the Blocks CSS plugin instead of one. Both editors are located in the same container.
Assumed Root Cause:
WordPress enables React StrictMode by default in the Block Editor.
React StrictMode runs useEffect hooks twice to detect potential side effects.
Analysis:
The Blocks CSS plugin initializes CodeMirror in a useEffect hook.
Since this useEffect doesn’t have a cleanup function that checks whether CodeMirror is already initialized, wp.CodeMirror() is called again on every mount cycle. With StrictMode enabled, this means: twice on the same DOM element.
Probable Solution:
The useEffect hook should implement a cleanup function that prevents CodeMirror from being initialized multiple times on the same element.
Side Notes:
This only happens in some of my setups.
I couldn’t figure out any possibly conflicting theme, plugin or code snippet. So I assume it might be something like a timing issue.
Conclusion:
I won’t change the 5-star rating, because despite of this problem the plugin does its job.
And I know how to handle this issue by a simple CSS rule to hide all Block CSS CodeMirrors except the last one:#o-css-editor .CodeMirror:not(:last-child) {
display: none;
}
Отличный плагин
Очень классные возможности! Пользуюсь постоянно!
“Essential, Useful Tool, Completes the Block Editor, Should be part of the core,” The one thing they don’t mention is how quick and genuinely concerned the support is.
Does exactly what I need it to do.
| WordPress | 6.2+ requiredTested up to 6.9.4 |
| PHP | 5.4+ required |
You can check the changelog here.
Plugin data sourced from WordPress.org. Analysis and metrics by PluginSift.