Jonathan Desrosiers

Linchpin

Aaron Ware

Note: This plugin does not support the block editor but should continue to work without issue when using it with custom post types and the <a href="https://wordpress.org/plugins/classic-editor/" rel="ugc">Classic Editor Plugin</a>.
Before WordPress displays a post’s content, the content gets passed through multiple filters to ensure that it safely appears how you enter it within the editor.
One of these filters is <a href="https://codex.wordpress.org/Function_Reference/wpautop" title="wpautop" rel="nofollow ugc">wpautop</a>, which replaces double line breaks with <code></code> tags, and single line breaks with <code> </code> tags. However, this filter sometimes causes issues when you are inputting a lot of HTML markup in the post editor.
This plugin displays a checkbox in the publish meta box of the post edit screen that disables the <a href="https://codex.wordpress.org/Function_Reference/wpautop" title="wpautop" rel="nofollow ugc">wpautop</a> filter for that post.
Also adds a ‘wpautop’, or ‘no-wpautop’ class to the post_class filter to help with CSS styling.

Toggle wpautop

Easily disable the default wpautop filter on a post by post basis.

MarcusPope

J-Ro

Azragh

This plugin preserves the user-generated HTML markup in the TinyMCE editor. Unlike other plugins this one allows developers to work in the HTML tab AND end-users to work in the WYSIWYG Visual tab at the same time! No longer will your HTML markup be completely munged into an unrecognizable form when you switch between those tabs. And you don’t have to hang your users/editors out to dry when you hand off the project with a disabled Visual tab.
<h4>IMPORTANT: Please read the installation instructions carefully. If you have existing content it will not render properly after activating this plugin until you use the Fix It Tools.</h4>
(One user didn’t read or follow these steps and panicked thinking I ruined their website.)
It also supports HTML5 Block Anchor tags in addition to other HTML5 elements, something that is currently not supported in WordPress via any existing plugins.

Preserved HTML Editor Markup Plus

Preserves HTML and developer edits in HTML AND WYSIWYG tab.  Supports inline scripts/css, JavaScript code blocks and HTML5 content editing

Toggle wpautop vs Preserved HTML Editor Markup Plus