Highlight

The highlight feature lets you mark text fragments with different colors. You can use it both as a marker (to change the background color) and as a pen (to change the text color).

Select the text you want to highlight. Then use the highlight toolbar button to choose a desired color from the dropdown.

After installing the editor, add the feature to your plugin list and toolbar configuration:

import { ClassicEditor, Highlight } from 'ckeditor5';

ClassicEditor
	.create( document.querySelector( '#editor' ), {
		licenseKey: '<YOUR_LICENSE_KEY>', // Or 'GPL'.
		plugins: [ Highlight, /* ... */ ],
		toolbar: [ 'highlight', /* ... */ ]
		highlight: {
			// Configuration.
		}
	} )
	.then( /* ... */ )
	.catch( /* ... */ );

const { ClassicEditor, Highlight } = CKEDITOR;

ClassicEditor
	.create( document.querySelector( '#editor' ), {
		licenseKey: '<YOUR_LICENSE_KEY>',
		plugins: [ Highlight, /* ... */ ],
		toolbar: [ 'highlight', /* ... */ ]
		highlight: {
			// Configuration.
		}
	} )
	.then( /* ... */ )
	.catch( /* ... */ );

The highlight feature comes with flexible configuration options.

However, the plugin has a predefined and limited number of available colors. It also focuses more on functionality than aesthetics. To change the text and background colors, use the font color and background color plugin.

The highlight feature uses inline <mark> elements in the view.

You can configure which highlight options are supported by the editor. Use the highlight.options configuration and define your highlight styles.

For example, the following editor supports two styles (a green marker and a red pen):

ClassicEditor
    .create( document.querySelector( '#editor' ), {
        // ... Other configuration options ...
        highlight: {
            options: [
                {
                    model: 'greenMarker',
                    class: 'marker-green',
                    title: 'Green marker',
                    color: 'var(--ck-content-highlight-marker-green)',
                    type: 'marker'
                },
                {
                    model: 'redPen',
                    class: 'pen-red',
                    title: 'Red pen',
                    color: 'var(--ck-content-highlight-pen-red)',
                    type: 'pen'
                }
            ]
        }
    } )
    .then( /* ... */ )
    .catch( /* ... */ );

Instead of using the (default) 'highlight' button, the feature also supports a configuration with separate buttons available directly in the toolbar:

ClassicEditor
    .create( document.querySelector( '#editor' ), {
        // ... Other configuration options ...
        toolbar: {
            items: [
                'heading',
                '|',
                'highlight:yellowMarker', 'highlight:greenMarker', 'highlight:pinkMarker',
                'highlight:greenPen', 'highlight:redPen', 'removeHighlight',
                '|',
                'undo', 'redo'
            ]
        }
    } )
    .then( /* ... */ )
    .catch( /* ... */ );

The highlight feature is using the power of CSS variables defined in the style sheet. Thanks to that, both the UI and the content styles share the same color definitions that you can customize:

:root {
    /* Make green a little darker. */
    --ck-content-highlight-marker-green: #199c19;

    /* Make the yellow more "dirty". */
    --ck-content-highlight-marker-yellow: #cac407;

    /* Make red more pinkish. */
    --ck-content-highlight-pen-red: #ec3e6e;
}

You can use inline color values in the rgba(R, G, B, A), #RRGGBB[AA], or hsla(H, S, L, A) formats instead of CSS variables. To do that, customize the options and define the color property for each option:

ClassicEditor
    .create( document.querySelector( '#editor' ), {
        // ... Other configuration options ...
        highlight: {
            options: [
                {
                    model: 'greenMarker',
                    class: 'marker-green',
                    title: 'Green marker',
                    color: 'rgb(25, 156, 25)',
                    type: 'marker'
                },
                {
                    model: 'yellowMarker',
                    class: 'marker-yellow',
                    title: 'Yellow marker',
                    color: '#cac407',
                    type: 'marker'
                },
                {
                    model: 'redPen',
                    class: 'pen-red',
                    title: 'Red pen',
                    color: 'hsl(343, 82%, 58%)',
                    type: 'pen'
                }
            ]
        }
    } )
    .then( /* ... */ )
    .catch( /* ... */ );

Then, update the classes in the style sheet so the content corresponds to the UI of the editor. The UI buttons and the actual highlights in the text should be the same color.

.marker-green {
    background-color: rgb(25, 156, 25);
}
.marker-yellow {
    background-color: #cac407;
}
.pen-red {
    color: hsl(343, 82%, 58%);
}

CKEditor 5 has more features that can help you style your content:

• Styles – Apply pre-configured styles like highlight or spoiler to existing content elements.
• Basic text styles – The essentials, like bold, italic, and others.
• Font styles – Control the font family, size, text or background color.
• Format painter – Easily copy text formatting and apply it in a different place in the edited document.
• Block quote – Include block quotations or pull quotes in your rich-text content.
• Remove format – Easily clean basic text formatting.

The Highlight plugin registers:

• The 'highlight' dropdown.

• The 'highlight' command.

  The number of options and their names correspond to the highlight.options configuration option.

  You can change the highlight of the current selection by executing the command with a desired value:

  editor.execute( 'highlight', { value: 'yellowMarker' } );
  

  Copy code

  The value corresponds to the model property in the configuration object. For the default configuration:

  highlight.options = [
      { model: 'yellowMarker', class: 'marker-yellow', title: 'Yellow Marker', color: 'var(--ck-content-highlight-marker-yellow)', type: 'marker' },
      { model: 'greenMarker', class: 'marker-green', title: 'Green marker', color: 'var(--ck-content-highlight-marker-green)', type: 'marker' },
      { model: 'pinkMarker', class: 'marker-pink', title: 'Pink marker', color: 'var(--ck-content-highlight-marker-pink)', type: 'marker' },
      { model: 'blueMarker', class: 'marker-blue', title: 'Blue marker', color: 'var(--ck-content-highlight-marker-blue)', type: 'marker' },
      { model: 'redPen', class: 'pen-red', title: 'Red pen', color: 'var(--ck-content-highlight-pen-red)', type: 'pen' },
      { model: 'greenPen', class: 'pen-green', title: 'Green pen', color: 'var(--ck-content-highlight-pen-green)', type: 'pen' }
  ]
  

  Copy code

  the 'highlight' command will accept the corresponding strings as values:

  • 'yellowMarker' – available as the 'highlight:yellowMarker' button,
  • 'greenMarker' – available as the 'highlight:greenMarker' button,
  • 'pinkMarker' – available as the 'highlight:pinkMarker' button,
  • 'blueMarker' – available as the 'highlight:blueMarker' button,
  • 'redPen' – available as the 'highlight:redPen' button,
  • 'greenPen' – available as the 'highlight:greenPen' button.

  Passing an empty value will remove any highlight attribute from the selection:

  editor.execute( 'highlight' );
  

  Copy code

The source code of the feature is available on GitHub at https://github.com/ckeditor/ckeditor5/tree/master/packages/ckeditor5-highlight.