Customize your WordPress site’s appearance by easily adding custom CSS and JS code without even having to modify your theme or plugin files. This is perfect to tweak your site.
Often when a theme or plugin updates it overwrites an old version of styles. That means anything you’d customized right in the code would be lost, potentially breaking your site depending on just what you’d changed. WordPress Easy Custom JS & CSS plugin lets you add custom javascript code, CSS custom styles, HTML markup to your site separately.
If you don’t use a child theme and need to insert some customizations, you can take advantage of the inbuilt editor and easily create and insert custom CSS and js code into the header or footer. Once the code is saved, it immediately influences the workings of your site.
Since the code contained within the plugin is separate from your theme, it will be unaffected by the theme updating. If you do break something playing around, all you have to do is go back into the plugin interface and change the wrong item.
Feature List

The code editor with syntax highlighting
The rich filter builder to construct inclusion rules
Include custom CSS and js code on the basis of a filter
Use inline embed method or include code as an external file
Custom CSS and js code can be in the header or footer area
Use custom javascript code and CSS styles inside the user or admin side or both
Minify javascript code and CSS styles to reduce the file size
Support SCSS and LESS preprocessors
All editors use AJAX saving to avoid reloading
Create as many codes as you want
The code is served from the filesystem instead of the database for better performance
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