redcocker

<p>Just another code syntaxhighligher for the theme and plugin editor with CodeMirror. This plugin can highlight sourcecodes in the theme/plugin editor and provide a useful toolbar.</p>
<h4>Features</h4>
<ul>
<li>Highlight sourcecodes in theme and plugin editor on the dashboard.</li>
<li>Based on Marijn Haverbeke’s “<a href="http://codemirror.net/" title="CodeMirrorr" rel="nofollow ugc">CodeMirror</a>” JavaScript library.</li>
<li>Built-in 10 themes.</li>
<li>Useful toolbar which includes search/replace features.</li>
<li>Full-screen editing.</li>
<li>Auto-complete.</li>
<li>Easy to configure features through the setting panel.</li>
<li>Localization: English(Default), 日本語(Japanese, UTF-8).</li>
</ul>
<h4>Support languages</h4>
<ul>
<li>PHP</li>
<li>CSS</li>
<li>Javascript</li>
<li>(X)HTML</li>
</ul>
<h4>Recommended plugin</h4>
<ul>
<li>“<a href="https://wordpress.org/extend/plugins/wp-syntaxhighlighter/" title="WP SyntaxHighlighter" rel="ugc">WP SyntaxHighlighter</a>” can highlight sourcecodes on your front-end(posts, pages, comments).</li>
</ul>


CodeMirror for CodeEditor

Just another code syntaxhighligher for the theme and plugin editor with CodeMirror.

seothemes

<p>HTML Widget adds a new widget that can be used for displaying any custom HTML in a easy to use way. The syntax highlighting makes the code clear and readable which makes your widgets easier to manage. Only users with sufficient capabilities can use all HTML elements, while users with limited capabilities can only use safe HTML that is allowed in posts.</p>


HTML Widget

This plugin replaces the lost functionality that the updated Text widget took away and it ends up being better than the one coming into core in 4.8.1 by adding syntax highlighting and autocompletion.

Better than core

Adds a simple HTML widget with syntax highlighting for HTML, CSS and JS.

CodeMirror for CodeEditor vs HTML Widget