How To Add Custom Editor Styles to Gutenberg


Adding Custom Gutenberg editor styles in WordPress is a nice touch to any theme, as it allows authors to get a basic preview of their content before it gets published. It seems like a complicated task, but it’s actually pretty simple, once you get started.


Default Gutenberg Editor Styles


Custom Gutenberg Editor Styles


It begins with registering and enqueueing a CSS file in your theme.

* Enqueue the Gutenberg editor stylesheet.
* Put this in your functions.php.
* @action enqueue_block_editor_assets
function jr3_enqueue_gutenberg() {
// Make sure you link this to your actual file.
wp_register_style( 'jr3-gutenberg', get_stylesheet_directory_uri() . '/css/editor.css' );
wp_enqueue_style( 'jr3-gutenberg' );
// This font is enqueued for the demo only. You probably won't need this.
wp_register_style( 'jr3-webfonts', '; );
wp_enqueue_style( 'jr3-webfonts' );
add_action( 'enqueue_block_editor_assets', 'jr3_enqueue_gutenberg' );


The CSS is a bit trickier because there are so many blocks and elements to cover. Here is an example that I’ve put together for this demo that can be a starting place for you.

/* Custom Editor Styles */
* With some edits, this can be used as a base for your Custom Editor Styles.
* Note that this is for demonstration purposes only, and some elements may not
* be covered here.
/* Approximate the theme width, except for full-width images. */
.wp-block:not( '.editor-block-list__block["data=full"]' ) {
width: 95%;
max-width: 1000px;
/* Fonts */
/* Note that Montserrat is enqueued in the PHP function that enqueues this file */
.editor-writing-flow .wp-block textarea,
.editor-writing-flow .wp-block .wp-block-freeform,
.editor-rich-text p,
.wp-block-quote__citation {
font-family: 'Montserrat', Arial, Helvetica, sans-serif;
/* TinyMCE Editor */
.editor-styles-wrapper p,
.editor-rich-text p,
.editor-styles-wrapper blockquote {
font-size: 16px;
line-height: 22px !important;
.editor-writing-flow .wp-block a {
color: #00a2ad !important;
/* Headings */
.editor-writing-flow .wp-block h1,
.editor-writing-flow .wp-block h3,
.editor-writing-flow .wp-block h3{
font-weight: bold;
.editor-writing-flow .wp-block h1 {
font-size: 36px;
line-height: 1.5em;
.editor-writing-flow .wp-block h2 {
font-size: 25px;
line-height: 1.5em;
.editor-writing-flow .wp-block h3 {
font-size: 16px;
line-height: 1.5em;
/* The Post Title */
.editor-post-title__block .editor-post-title__input {
color: #00a2ad;
text-align: center;
/* Blockquote styles */
.wp-block blockquote {
font-style: italic;
color: #aaa;
margin-left: 20px;
border-left: 0;
padding-left: 0;
.wp-block blockquote .editor-rich-text {
padding-left: 3rem;
.wp-block blockquote:before {
color: #ccc;
content: '\201C' !important;
font-size: 4em;
position: absolute;
top: 10px;
.wp-block-quote:not(.is-large):not(.is-style-large) {
border-left: 0;
margin-left: 0;
padding-left: 0;

How to Add Full Width Images in Gutenberg

Theme Preview with a Full-Width Image

Full width images are a sweet new feature that Gutenberg offers to WordPress theme developers. In order to enable these in your theme, it takes just a few lines of code.

Problem #1

By default, the Gutenberg Image Block only has the three classic alignment options: left-aligned, centered, and right-aligned.

Gutenberg Default Image Alignment Options
Gutenberg Default Image Alignment Options

Enabling Wide Images in the Gutenberg Editor

First, a bit of PHP.  Add this to your theme’s functions.php, or wherever else you are adding your add_theme_support() functions.

* Add Theme Support for wide and full-width images.
* Add this to your theme's functions.php, or wherever else
* you are adding your add_theme_support() functions.
* @action after_setup_theme
function jr3_theme_setup() {
add_theme_support( 'align-wide' );
add_action( 'after_setup_theme', 'jr3_theme_setup' );

Now, you can find two new icons on your Image Gutenberg Block, wide-align, and full-width.

Gutenberg Image Block Updated Options

When one of these options is selected, it will display correctly in the editor.  If you select wide-align, the image gets wider, and if you select full-width, the image fills the editor horizontally.

Wide Image Previews in the Gutenberg Editor

Gutenberg Image Block Wide Width in the Editor
A wide image in the Gutenberg Editor
Gutenberg Image Block Full Width in the Editor
A full-width image in the Gutenberg Editor

Problem #2

There’s just one issue: Although WordPress adds special classes to the image markup, this doesn’t affect your actual theme styles.

Gutenberg Image in the Theme, unstyled
An unstyled full-width image in the Theme.

The Solution

To solve this, add your own CSS.  Here’s a snippet I came up with:

.alignwide {
/* Set these margins to work with your own theme. */
margin-left: -80px;
margin-right: -80px;
max-width: 100vw;
.alignfull {
margin-left: calc(-100vw / 2 + 100% / 2);
margin-right: calc(-100vw / 2 + 100% / 2);
max-width: 100vw;
.alignfull img {
width: 100vw;

A few notes about the CSS:

  • calc() tells the browser to calculate a value (usually) based on the screen size.
  • vw refers to “viewport width,” or screen width.

The Result

After the styles are applied:

Gutenberg Wide Image in the Theme
A wide-aligned image in the theme after adding the CSS.
A full-width image in the theme after adding the CSS.
A full-width image in the theme after adding the CSS.

So, with less than 20 lines of code, you can add this powerful and attractive feature to your themes.

Further Reading