Instructions copied from MDL-75963 . Verify lib version Access to "Site administration / Development / Third party libraries". Verify third-party lib versions for PrismJs is 1.29.0 Verify important upgrade steps were followed Verify the following command returns no results grep 'code\[class\*="language-"\]' filter /codehighlighter/styles .css Verify code highlighting works Log in as admin. Navigate to Manage Filters in Site Admin Verify that you see "Code Highlighter" in the filter table, and enable the filter. Choose TinyMCE as your text editor by navigating to Editor Preferences. Navigate to Edit Profile. In the description input, fill in the text "This code text should be red". Block the text. Click Format on the menu and select Code. Verify that the text colour turns red. Click the Update Profile button. Navigate to your Profile page. Verify that the text is displayed in the same style as the TinyMCE editor. Navigate to Edit Profile. Create a new line at the bottom of the previous text in the description input. Click Insert on the menu and select Code Sample. Select "PHP" in the language dropdown. In the code view, fill in the text below: <?php defined( 'MOODLE_INTERNAL' ) || die(); ?> Click the Save button. Verify if you see the code written with the code highlighter display. Click the Update Profile button. Navigate to your Profile page. Verify that the profile description has the text "This code text should be red" and the PHP line of codes with the same look/style as the TinyMCE editor.