ACF Blocks Configuration via block.json

Last updated May 22, 2024


Since ACF 6.0, ACF has recommended using block.json to handle your block registration.

A mirror of the WordPress JSON Schema for block.json, with ACF’s additions, is available at

The WordPress documentation for block.json, describing all the core properties, is available here.

If your block.json contains an ACF key, it will be loaded by ACF as an ACF Block.

Block.json ACF Key

The ACF key supports the following properties:

  • renderTemplate
    (String) The path to a template file used to render the block HTML. This can either be a relative path from the block.json file or a full path to any file.

    // Specifying a relative path to the block.json file
    "acf": {
    "renderTemplate": "testimonial.php"
  • renderCallback
    (Callable) (Optional) Instead of providing a render template, a callback function name may be specified to output the block’s HTML.

    // Specifying a function
    "acf": {
    "renderCallback": "my_acf_block_render_callback"
  • mode
    (String) (Optional) The display mode for your block. Available settings are “auto”, “preview” and “edit”. Defaults to “preview”.

    • auto: Preview is shown by default, but changes to edit form when block is selected.
    • preview: Preview is always shown. Edit form appears in sidebar when block is selected.
    • edit: Edit form is always shown.
    Note: When in “preview” or “edit” modes, an icon will appear in the block toolbar to toggle between modes.
    "acf": {
    "mode": "auto"
  • blockVersion
    (Integer) The version of ACF Blocks to use. Version 1 of ACF Blocks is deprecated and not recommended for use with block.json. Default is 2.

  • postTypes
    (Array) (Optional) An array of post types to which this block type is restricted.

    "acf": {
    "postTypes": ["post", "page"]
  • validate (Boolean) (Since 6.3.0) Should the fields in the block be validated as per the field group configuration. Default is true.

    "acf": {
    "validate": false
  • usePostMeta (Boolean) (Since 6.3.0) Should this block store its field values directly in post meta, rather than the block comment. When enabled, this block will be limited to once per page, and only as a top level block. These blocks will also not be supported as widgets or in the site editor/templates. Default is false.

    "acf": {
    "usePostMeta": true

Block.json Example

    "name": "acf/testimonial",
    "title": "Testimonial",
    "description": "A custom testimonial block that uses ACF fields.",
    "style": [ "file:./testimonial.css" ],
    "category": "formatting",
    "icon": "admin-comments",
    "keywords": ["testimonial", "quote"],
    "acf": {
        "mode": "preview",
        "renderTemplate": "testimonial.php",
        "validate": "false"
    "supports": {
        "anchor": true