New Feature: The Block Bindings API

WordPress 6.5 is introducing a new way of extending blocks that substantially reduces the custom code needed to integrate different kinds of data in the blockBlock Block is the abstract term used to describe units of markup that, composed together, form the content or layout of a webpage using the WordPress editor. The idea combines concepts of what in the past may have achieved with shortcodes, custom HTML, and embed discovery into a single consistent API and user experience. editor.

This can now be done through the new Block Bindings APIAPI An API or Application Programming Interface is a software intermediary that allows programs to interact with each other and share data in limited, clearly defined ways..

What is the Block Bindings API?

Given a coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress. block, rather than displaying a user’s inline written content inside of it, imagine wanting to populate that block with data from a particular source instead. For example, the post metadata or custom PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher logic. What would be the process for doing that?

Screenshot showing a heading and paragraph in the Gutenberg editor, with a large red arrow pointing to the paragraph. The paragraph reads: "How would you replace this sentence with data from somewhere else?"

This is actually a trick question: In previous versions of WordPress, you were unable to do this with GutenbergGutenberg The Gutenberg project is the new Editor Interface for WordPress. The editor improves the process and experience of creating new content, making writing rich content much simpler. It uses ‘blocks’ to add richness rather than shortcodes, custom HTML etc.’s core blocks — it would instead require creating a custom block with particular logic for reading from the source in question. But this is no longer the case.

With the Block Bindings API, you can now bind core blocks to read from different sources without needing to write custom block boilerplate — this means it is possible to bind a Paragraph to read from a post’s metadata, or a Heading to read from a pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the Plugin Directory or can be cost-based plugin from a third-party’s PHP logic, all without needing to deal with ReactReact React is a JavaScript library that makes it easy to reason about, construct, and maintain stateless and stateful user interfaces., block registration, and other particulars of writing custom blocks from scratch for each new source you want to read from.

This initial release of the Block Bindings API in WordPress 6.5 is a big step towards simplifying the process of extending the editor and expanding the capabilities of blocks. Under the hood, the API already powers a showcase feature being shipped in WordPress 6.5 alongside it: Connecting core blocks to custom fields in the post metadata.

Using the same functionality, as an advanced use case, it is also possible to define and have blocks read from custom sources — more on that briefly below.

Note: For a more detailed walkthrough on creating and using Block Bindings than can be related in this brief dev notedev note Each important change in WordPress Core is documented in a developers note, (usually called dev note). Good dev notes generally include a description of the change, the decision that led to this change, and a description of how developers are supposed to work with that change. Dev notes are published on Make/Core blog during the beta phase of WordPress release cycle. Publishing dev notes is particularly important when plugin/theme authors and WordPress developers need to be aware of those changes.In general, all dev notes are compiled into a Field Guide at the beginning of the release candidate phase., see the Introducing Block Bindings tutorial from the WordPress Developer Blogblog (versus network, site).

How do block bindings work?


Before getting into the rich functionality Block Bindings can enable via custom sources, this section will first review how the API works in general, then detail how to bind core blocks to custom fields in the post metadata.

The following table shows the current compatible blocks and attributes that can be bound: 

Supported BlocksSupported Attributes
Imageurl, alt, title
Buttonurl, text, linkTarget, rel

While the list of compatibility is short for now, this already enables a wide range of use cases, and support for the rest of the core blocks, as well as custom blocks, is planned for the future.

To use Block Bindings, you would specify that these attributes should be read from particular registered sources using the block markup; the logic for those sources would then be executed when rendering on the frontend.

Upon being bound, editing of the attribute in question will be locked and indicators will appear in the editor to signal that the binding has been created.

Screenshot of the Gutenberg editor; a paragraph is selected and there are icons in the block toolbar, as well as a purple outline around the paragraph, declaring the block as bound.

Specifically, here is how to make use of this via the built-in custom fields support.

Custom fields

Importantly, in this first version of the Block Bindings API, there is no UIUI User interface for binding attributes to custom fields yet. Therefore, it is necessary to add the markup manually using the Code Editor in Gutenberg.

To bind a supported attribute to a custom fieldCustom Field Custom Field, also referred to as post meta, is a feature in WordPress. It allows users to add additional information when writing a post, eg contributors’ names, auth. WordPress stores this information as metadata. Users can display this meta data by using template tags in their WordPress themes. in the post metadata, you would use markup such as the following:

<!-- wp:paragraph {
} -->
<!-- /wp:paragraph -->

In order for this to work, you would need to make sure the field is registered to the post metadata by including code such as the following in the theme’s functions.php or a plugin.

'show_in_rest' => true,
'single' => true,
'type' => 'string',
'default' => 'Default text field',

*Note that the show_in_rest property must be set to true for the time being due to security considerations, though there are plans to explore how to remove this requirement in the future.

Future sources

Support for post metadata is just a start, and the plan is to add more built-in sources, such as site, user, and taxonomyTaxonomy A taxonomy is a way to group things together. In WordPress, some common taxonomies are category, link, tag, or post format. data, for WordPress 6.6.

That being said, the Block Bindings API already has the functionality to allow for registering of custom sources as well, which is the same functionality used internally to register the core/post-meta source above.

Registering a custom source


To register a Block Bindings source, one needs to use the register_block_bindings_source() function, which has the following signature:

string $source_name,
array $source_properties

There are two available parameters:

  • $source_name: A unique name for the custom binding source in the form of namespace/slug. The namespace is required.
  • $source_properties: An array of properties to define the binding source:
    • label: An internationalized text string to represent the binding source. Note: this is not currently shown anywhere in the UI.
    • get_value_callback: A PHP callable (function, closure, etc.) that is called when a block’s bound attribute source matches the $source_name parameter.
    • uses_context: (Optional) Extends the block instance with an array of contexts if needed for the callback. For example, to use the current post ID, it should be set to [ 'postId' ].

When WordPress encounters the custom bindings source while parsing a block, it will run the get_value_callback function, whose signature should look like this:

array $source_args,
WP_Block $block_instance,
string $attribute_name

It can accept up to three parameters, though you don’t need to include them unless your logic requires them:

  • $source_args: An array of arguments passed via the metadata.bindings.$attribute.args property from the block.
  • $block_instance: The current instance of the block the binding is connected to as a WP_Block object.
  • $attribute_name: The current attribute set via the metadata.bindings.$attribute property key on the block.

Using the Registration Mechanism

In practice, here is how you might use the above registration function to create a simple binding for copyright information:

add_action( 'init', 'projectslug_register_block_bindings' );

function projectslug_register_block_bindings() {
register_block_bindings_source( 'projectslug/copyright', array(
'label' => __( 'Copyright', 'projectslug' ),
'get_value_callback' => 'projectslug_copyright_binding'
) );

function projectslug_copyright_binding() {
return '&copy; ' . date( 'Y' );

And here is how you would bind a paragraph to the copyright source in the block markup, and how it would look on the frontend:

<!-- wp:paragraph {
} -->
<p>Copyright Block</p>
<!-- /wp:paragraph -->
A screenshot of a post titled "Block Bindings Copyright Example"; in the content is a copyright symbol and the year 2024.

Of course, this is a simple example, and you could make use of the other parameters in the callback signature to create more extensive logic.

Additional API functions

Additionally, there are a few other functions currently part of the public API:

  • unregister_block_bindings_source( $string source_name ): Unregisters a source
  • get_all_registered_block_bindings_sources(): Gets all registered sources
  • get_block_bindings_source( $string source_name ): Retrieves a registered source

Also, please note that while the core sources use shared APIs in the editor UI, be aware that these editor APIs will remain private for the time being while discussion continues on how to standardize extensions to the UI around this feature.

This means that if you would like to implement a UI to handle your custom fields easily, for now, you will need to create that functionality yourself.

Further learning and next steps

For more inspiration on how to use Block Bindings in your own projects, see the registration logic in block-bindings.php and the built-in core/post-meta source, and take a look at the Introducing Block Bindings tutorial series.

With that in mind, Block Bindings are just getting started, and future plans include:

  • Add the possibility of editing the value of the metaMeta Meta is a term that refers to the inside workings of a group. For us, this is the team that works on internal WordPress sites like WordCamp Central and Make WordPress. fields directly from the UI.
  • Add UI to allow users to add bindings through the Editor.
  • Create new built-in sources: Site data, post data, and taxonomy data.
  • Add support for more core blocks.
  • Add the ability for developers to extend the Editor UI.

As always, feedback is more than welcome, and we invite you to share your ideas and use cases on Github, this post, or WordPress SlackSlack Slack is a Collaborative Group Chat Platform The WordPress community has its own Slack Channel at to help shape the development of the Block Bindings API.

A big thanks to @greenshady for providing code snippets and the initial ideas for this post, as well as @santosguillamot, and @czapla for offering their feedback.

#6-5, #dev-notes, #dev-notes-6-5