Klaylton Fernando

This plugin adds 3 fields on every page and blog post where you can type your code in a readable interface.
In addition to being very light and functional, the WP Custom Code plugin also allows you to work with external libraries. Basque paste the address 
of the javascript library of your choice in the designated field and you will be able to enjoy this indispensable resource.

WP Custom Code

Add CSS and Javascript to your pages simply and quickly. WP Custom Code supports CodeMirror.

salubrio

Intended users: Template Designers, Developer
If you wish to add any custom HTML to the bottom of each page’s head, then this plugin is for you. For example, you can add some custom CSS, a link to an external javascript file or something else.
The problem with editing the template directly is if you ever update the template, your changes will be lost. This plugin works around this issue.
<h3>Acknowledgements</h3>
Plugin Icon (CC BY 3.0) by <a href="https://www.iconfinder.com/denir" rel="nofollow ugc">DeniShop</a>

Add Code To Head

Add custom Javascript/HTML/CSS codes to the page head without editing the template.

WP Custom Code vs Add Code To Head