What’s New With ACF Blocks in ACF 6

Last updated Aug 17, 2023


ACF 6.0 includes ACF Blocks Version 2. This next generation of ACF Blocks brings us much closer to the native block experience, while still giving you the PHP based templating language you know as a WordPress developer.

In the last few releases of WordPress, Gutenberg has made significant changes to all aspects of the block editor and block registration, and this has impacted ACF Blocks. We’ve not been able to move as fast as we would have liked on implementing changes to support these new features for back compatibility reasons. ACF 6.0 ships with a new block versioning system, allowing you to opt in to new versions which will change things like the markup and structure of ACF Blocks in both the backend and frontend, and may require updates to your theme to support.

Backwards Compatibility

The changes to blocks in ACF 6.0 are designed to be backwards compatible with ACF 5.x, with one notable exception. Due to the changes in block IDs, if you use parse_blocks() to read data from an ACF Block, it will no longer have a block ID present in that data. For workarounds to this, see our examples for adding a block ID back in.

Whilst we recommend users upgrade to block.json blocks to take advantage of new and upcoming WordPress features if they can, blocks registered with acf_register_block_type() will continue to work with ACF 6.

Block.json Support

Since WordPress 5.8, WordPress has supported – and recommended – that blocks are registered through a JSON configuration file. All of the WordPress Block Documentation was migrated to only show block.json configuration objects, and it became confusing for users to know what WordPress configuration options were usable in ACF PRO. ACF 6.0 introduces support for block.json registration of blocks with ACF.

For blocks registered through a block.json file, you can mark them as ACF Blocks by adding a new ACF configuration key to the JSON file, which contains the ACF specific configuration, for example:

    "name": "all-fields-block",
    "title": "All Fields Test Block",
    "description": "All fields test block",
    "style": "file:./all-fields-block.css",
    "category": "theme",
    "icon": "admin-comments",
    "apiVersion": 2,
    "keywords": [
    "acf": {
        "mode": "preview",
        "renderTemplate": "all-fields-block.php",
        "postTypes": [ "post" ]
    "styles": [
        { "name": "default", "label": "Default", "isDefault": true },
        { "name": "red", "label": "Red" },
        { "name": "green", "label": "Green" },
        { "name": "blue", "label": "Blue" }
    "supports": {
        "align": true,
        "anchor": true,
        "alignContent": false,
        "color": {
            "text": true,
            "background": true,
            "link": true
        "alignText": true,
        "spacing": {
            "margin": [
            "padding": true
        "typography": {
            "lineHeight": true,
            "fontSize": true
        "fullHeight": true
    "attributes": {
        "backgroundColor": {
            "type": "string",
            "default": "purple"
    "example": {
        "attributes": {
            "data": {
                "text": "This is an example text field",
                "text_area": "This is an example text area field"

You then need to use the standard WordPress block registration function register_block_type, rather than acf_register_block_type:

register_block_type( 'path/to/folder/containing/block.json' );

If you don’t specify a namespace for your block like in our example above: "name": "all-fields-block",, ACF will automatically add it if it is an ACF block to become the equivalent of "name": "acf/all-fields-block" although you are now free to use your own namespace for your blocks.

This new method of registering blocks is now the recommended way to register a block, replacing the acf_register_block_type function.

The renderTemplate property should either be a full path to the template file, or relative to the location of the JSON file.

You can also now specify default attributes for your block, as shown in our example above in the attributes key. You can use this to set defaults for the WordPress provided block attributes, such as backgroundColor.

WordPress uses a camelCase format inside JSON files, and ACF adopts that too. Configuration keys such as render_template when used in acf_register_block_type need to be renderTemplate when used in JSON, likewise align_content and full_height should be alignContent and fullHeight for example. All previous configuration objects are supported, except for enqueue_style, enqueue_script and enqueue_assets for reasons explained below:

Block Asset Loading

When ACF Blocks was first introduced, it supported enqueueing block specific assets before WordPress had native support. Recent (and upcoming) updates to Gutenberg will require these assets to be loaded using specific WordPress asset configuration keys such as editorScript, script, editorStyle and style.

WordPress 5.9 users who use Block Styles may have noticed that the ACF registration of styles was not applied to those previews, which is why all ACF Block users should migrate their blocks to use those WordPress provided methods of asset loading.

The previous methods of asset loading in ACF Blocks will continue to work for the time being in acf_register_block_type, but as WordPress continues to make changes across releases we expect that to stop working – especially with the upcoming plan to isolate each block in an iframe.

Block ID Changes

ACF 6.0 will no longer save block IDs to the block comment of ACF Blocks. This affects all versions of ACF Blocks and means you can easily copy and paste blocks, simplify your post type templates, use your blocks in block patterns, or duplicate blocks without having any issues where block IDs clash.

This change shouldn’t affect most users, since we still generate a $block['id'] for your templates as we know some users use that for element IDs, but the format of those IDs will change. Just like in ACF 5.x, block IDs may be duplicated, but the number of situations where this can happen has been reduced significantly to one: if you have multiple blocks on the same page with the exact same data, attributes and context.

Due to the dynamic block ID generation, this change is backwards compatible for the majority of users, unless you use parse_blocks() to read ACF data, and rely on it returning a block ID.

Internally, ACF builds the new dynamic block ID from a md5 hash of the block’s attributes and context, but as WordPress block context may not be available in parse_blocks() so you will not reliably be able to match our dynamic block ID with the result of parse_blocks().

There are a couple of options to get around this. You could generate your own hash through a checksum of the sorted data attributes, use user entered anchors, or you could automatically generate an ID that is saved server side whenever a block is saved using the acf/pre_save_block filter.

Here’s a couple of possible examples, the first will automatically generate an anchor attribute if the user doesn’t enter one:

    function( $attributes ) {
        if ( empty( $attributes['anchor'] ) ) {
            $attributes['anchor'] = 'acf-block-' . uniqid();
        return $attributes;

Alternatively, you could generate a new custom ID attribute which would be used on the front-end too if set, but note that it will be regenerated each time the block is saved, and this id will not be used in the backend editor:

    function( $attributes ) {
        if ( empty( $attributes['id'] ) ) {
            $attributes['id'] = 'acf-block-' . uniqid();
        return $attributes;

Block Versioning Details

A new blockVersion (inside the ACF key in block.json) or acf_block_version (if using acf_register_block_type) key is now supported. For blocks registered via block.json, this defaults to 2. For acf_register_block_type, this defaults to 1.

For now, the main change between the two versions is the way <InnerBlocks /> markup is rendered. If you use block version 2 (which requires WordPress 5.8+), the container markup when using InnerBlocks will match between backend and frontend rendering, with any inner blocks wrapped in a new (and single level) <div class="acf-inner-blocks-container"></div> element. This can help make your CSS layouts easier, as you can be sure both render views have the same markup.

Whilst this wrapper must appear in the backend block editor, if you wish to disable it for the frontend, you can do that with a new filter, and optionally enable or disable it based on the block name:

add_filter( 'acf/blocks/wrap_frontend_innerblocks', 'acf_should_wrap_innerblocks', 10, 2 );
function acf_should_wrap_innerblocks( $wrap, $name ) {
    if ( $name == 'acf/test-block' ) {
        return true;
    return false;

If you just wish to modify the class being used for the wrapper, instead of the default acf-inner-blocks-container you can simply add a class to your <InnerBlocks /> tag inside your block template, such as …

<InnerBlocks class="test-wrapper-class second-class" />

Block Registry Standardization

In previous versions of ACF PRO, a lightweight shim of the block configuration was registered in PHP, and then the full configuration registered in JS.

In this build of ACF, the full block configuration is now saved in the WordPress PHP Block Registry. This makes it easier for you to access details of the block configuration in your templates or render callbacks.

Block Context Changes

During development, we saw a conversation on twitter discussing the viability of using data from an ACF Block inside blocks contained in its <InnerBlocks> children.

We suspected this would be possible using block context, the system core blocks like the Query Loop block use to know the current post type.

ACF 6.0 introduces support for block context. This means if you want to pass ACF field data from a parent block to an InnerBlock, the InnerBlock will automatically reload the template, showing changes live as you make changes to fields in the parent. This support should also improve the reliability of blocks used inside Query Loop blocks.

To enable this, you need to tell WordPress to share the ACF data attribute to its child blocks with a custom key (acf/fields in our example) with providesContext in block.json:

"providesContext": {"acf/fields": "data"}

Then, to consume that context in an ACF block, you need to pass the context key in usesContext:

"usesContext": ["acf/fields"],

One thing to note: ACF Blocks use field keys in the block editor, and block data is only hydrated to field names upon save. Because of this, you should use $context['acf/fields']['field_key'] to get access the data inside your template if it exists before defaulting back to $context['acf/fields']['field_name'] if it doesn’t exist to support both backend and frontend output of context data.

You should also be aware that if you share ACF data through to your child blocks, the full ACF fields data will be sent back to the server in order to render previews. This may have performance implications for your blocks in the editor.

Blocks Without Fields

With Full Site Editing and the Query Loop block, it’s now much more likely you might want to use ACF Blocks without any specific fields attached to the block, for example because it’s showing post templating elements like titles or post content, or because you want to display fields which are added on the post being displayed, rather than from the block.

ACF 6.0 adds support for this by providing advisory text when a block has no fields assigned, whereas previously the block’s edit mode would simply be blank and not selectable.

Developers who wish to modify the default advisory text can do so with the new acf/blocks/no_fields_assigned_message filter which offers 2 parameters: the message to be displayed and the name of the block it will be displayed on.

Block Bug Fixes

We’ve also fixed a number of other bugs which apply to all versions of ACF Blocks.

  • The render_block_preview JavaScript event is now always fired every time a block preview is displayed, rather than just the first time.
  • Accordion fields inside an ACF block now are styled to match the native sidebar experience of the block editor.
  • ACF Block preloading now works again for blocks saved in edit mode, and for blocks without any saved field data (due to changes in block preloading for the removal of Block IDs, you may need to edit each block once before it can be preloaded.)
  • ACF Block edit forms will now behave correctly if they’re not visible when loaded.