Junaid Bhura a web developer in Melbourne, Australia - specializing in WordPress development.

How to extend blocks in the Gutenberg editor on WordPress


This post assumes that you already know how to work with JavaScript ES6 and have some experience in working with and setting up custom blocks on WordPress using Webpack.

Gutenberg Blocks

With the introduction of WordPress 5, we now have a new powerful tool at our disposal: Blocks. Blocks let us build custom experiences in the WordPress editor, making it easier for content managers to write and maintain content on the website.

But there’s one big caveat though: They’re built using JavaScript. WordPress developers, who have strong PHP knowledge might find it a little difficult to transition if they are not familiar with JavaScript – and might reach out to tools like ACF Blocks. Although tools like this are useful in the short-term, you will pretty much have to learn things like React, if you really want deep control over the editor, and understand topics like the one discussed in this post.

My advice: Bite the bullet, spend some time and learn JavaScript. It’s totally worth it.

Block Filters

As with everything WordPress, blocks in JavaScript have filters too! We are going to be discussing them, by example, in this post:

Example: How to use block filters to add “Open in a new tab” to core buttons

Let me first show you the full source code – and then break it down below:


1. The blocks.registerBlockType filter

We use this filter to look for a core/button block and use the spread operator to add an attribute “target”:

target: {
 type: 'string',
 default: '',
 source: 'attribute',
 attribute: 'target',
 selector: 'a',

2. The editor.BlockEdit filter

We then use this filter to add a new panel with a ToggleControl control to work with the attribute “target” defined above. So you have a nice little toggle control in the editor to turn it off or on. If it’s on, we set the value “_blank” to the attribute, if not, we set an empty value.

3. The blocks.getSaveElement filter

This filter allows us to control the markup of the element before it’s saved. The markup, in turn, is controlled via a JavaScript object. We check if the attribute “target” has the value “_blank”, and if so – we set that to the element.

Notice we also set the value noreferrer noopener to the “rel” attribute. We do this to avoid an error in the editor, which specifically looks for this value for all links which have a target value set to “_blank”.

Caveat: Although the whole point of this filter is to modify the element, you… can’t modify it… directly? Which is why we use the cloneElement function, which essentially allows you to clone the original object and modify it instead.


I appreciate that this is a lot to take in if you’re just starting off, so I’d recommend doing a bit more reading in order to fully get a grasp of this. You can also use this same method to extend not only any core block, but any block at all!

Happy coding! 🙂

One response to “How to extend blocks in the Gutenberg editor on WordPress”

  1. Thank you for the tutorial. I was looking to accomplish something similar by extending the core/pullquote block. My goal is to have a toggle in the block inspector that allows you to add an optional button beneath the normal < blockquote > and < cite > HTML elements. I have the basics working to get the toggle to show up for the core/pullquote block and to have the extra markup appear via the blocks.getSaveElement. What I’m wondering is how to make the extra markup appear within the WordPress editor itself. If I edit the pullquote block on a page and toggle the newly added toggle button, no HTML changes are made in the editor. The only changes appear on the front-end. I am happy to send you a Gist for the code I’m working with if that’s helpful. Thanks.

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