How to Add Full Width Images in Gutenberg

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

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.

	<?php
	/**
	* 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' );

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

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

A wide image in the Gutenberg 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.

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;
	}

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full-width-image-theme-support.css
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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:

A wide-aligned 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

• WP.org developer docs, “wide-alignment”