Pavel

The “Light Code Block” plugin is a simple and lightweight solution for inserting and displaying code snippets in posts and pages. 
It works by adding a custom “LC” button to the TinyMCE (Classic) editor or a code block in the Gutenberg editor.
The inserted code will be shown on the front end in a clean, readable format.
<h3>Usage</h3>
<ul>
<li>Install and activate the plugin.</li>
<li>Go to the post or page edit screen.</li>
<li>In the TinyMCE (Classic) editor, click the “LC” button in the toolbar.</li>
<li>In the popup window that opens, paste or write your code, and click OK.</li>
<li>Save or update your post.</li>
</ul>
The code will be saved inside a special block and displayed on the front end within a <code><pre></code> tag with the class <code>mce-simple-code-block</code> (i.e., <code><pre class="mce-simple-code-block">...</pre></code>).
To insert code using the Gutenberg editor, you first need to add a Classic (TinyMCE) block, and then use it to insert your code.

Light Code Block

The "Light Code Block" plugin is the simplest and lightest plugin for inserting and displaying code.

michielve

There are other good syntax highlighter plugins, but I wanted something simple and fast and 
be able to add the highlight classes with a select box in the TinyMCE editor.
I added some default languages: Javascript, PHP, Python, C, C#, VB.NET, SQL and CSS but you can 
easily add other ones.

Simple Fast Highlighter

Fast syntax highlighter written in Javascript.

Light Code Block vs Simple Fast Highlighter