diff --git a/block-json/block.json b/block-json/block.json
new file mode 100644
index 0000000..3f3444e
--- /dev/null
+++ b/block-json/block.json
@@ -0,0 +1,34 @@
+{
+	"name": "my-plugin/notice",
+	"title": "Notice",
+	"category": "text",
+	"parent": [ "core/group" ],
+	"icon": "star",
+	"description": "Shows warning, error or success notices  ...",
+	"keywords": [ "alert", "message" ],
+	"textdomain": "my-plugin",
+	"attributes": {
+		"message": {
+			"type": "string",
+			"source": "html",
+			"selector": ".message"
+		}
+	},
+	"supports": {
+		"align": true,
+		"lightBlockWrapper": true
+	},
+	"styles": [
+		{ "name": "default", "label": "Default", "isDefault": true },
+		{ "name": "other", "label": "Other" }
+	],
+	"example": {
+		"attributes": {
+			"message": "This is a notice!"
+		}
+	},
+	"editorScript": "build/editor.js",
+	"script": "build/main.js",
+	"editorStyle": "build/editor.css",
+	"style": "build/style.css"
+}
diff --git a/block-json/class-parser.php b/block-json/class-parser.php
new file mode 100644
index 0000000..9a5f45e
--- /dev/null
+++ b/block-json/class-parser.php
@@ -0,0 +1,174 @@
+<?php
+
+namespace WordPressdotorg\Plugin_Directory\Block_JSON;
+
+use WP_Error;
+
+defined( 'WPINC' ) || die();
+
+/**
+ * Class Parser
+ *
+ * @package WordPressdotorg\Plugin_Directory\Block_JSON
+ */
+class Parser {
+	/**
+	 * A location resource must be pointing to a file named this.
+	 *
+	 * @const string
+	 */
+	const REQUIRED_FILENAME = 'block.json';
+
+	/**
+	 * Parse the JSON content of a given resource into a PHP object.
+	 *
+	 * @param array $resource An associative array with one item where the key specifies the type of resource and the
+	 *                        value represents the resource as a string. Valid types are `url`, `file`, and `content`.
+	 *                        In this case, the value of `content` is expected to be a raw string of JSON, while the
+	 *                        other two are expected to be the location of a file containing the JSON.
+	 *
+	 * @return object|WP_Error An object if the parse was successful, otherwise a WP_Error.
+	 */
+	public static function parse( array $resource ) {
+		reset( $resource );
+		$type   = key( $resource );
+		$handle = current( $resource );
+
+		switch ( $type ) {
+			case 'url':
+				$content = self::extract_content_from_url( $handle );
+				break;
+			case 'file':
+				$content = self::extract_content_from_file( $handle );
+				break;
+			case 'content':
+				$content = $handle;
+				break;
+			default:
+				$content = new WP_Error(
+					'no_valid_resource',
+					__( 'No valid resource type was given.', 'wporg-plugins' )
+				);
+				break;
+		}
+
+		if ( is_wp_error( $content ) ) {
+			return $content;
+		}
+
+		return self::parse_content( $content );
+	}
+
+	/**
+	 * Get the contents of a block.json file via an HTTP request to a URL.
+	 *
+	 * @param string $url
+	 *
+	 * @return string|WP_Error
+	 */
+	protected static function extract_content_from_url( $url ) {
+		$url = esc_url_raw( $url );
+
+		$filename_length = strlen( self::REQUIRED_FILENAME );
+		if ( strtolower( substr( $url, - $filename_length ) ) !== self::REQUIRED_FILENAME ) {
+			return new WP_Error(
+				'resource_url_invalid',
+				sprintf(
+					/* translators: %s: file name */
+					__( 'URL must end in %s!', 'wporg-plugins' ),
+					'<code>' . self::REQUIRED_FILENAME . '</code>'
+				)
+			);
+		}
+
+		$response      = wp_safe_remote_get( $url );
+		$response_code = wp_remote_retrieve_response_code( $response );
+
+		if ( is_wp_error( $response ) ) {
+			return $response;
+		} elseif ( 200 !== $response_code ) {
+			return new WP_Error(
+				'resource_url_unexpected_response',
+				__( 'URL returned an unexpected status code.', 'wporg-plugins' ),
+				array(
+					'status' => $response_code,
+				)
+			);
+		}
+
+		return wp_remote_retrieve_body( $response );
+	}
+
+	/**
+	 * Get the contents of a block.json file via a path in the filesystem.
+	 *
+	 * @param string $file
+	 *
+	 * @return string|WP_Error
+	 */
+	protected static function extract_content_from_file( $file ) {
+		$filename_length = strlen( self::REQUIRED_FILENAME );
+		if ( strtolower( substr( $file, - $filename_length ) ) !== self::REQUIRED_FILENAME ) {
+			return new WP_Error(
+				'resource_file_invalid',
+				sprintf(
+					/* translators: %s: file name */
+					__( 'File must be named %s!', 'wporg-plugins' ),
+					'<code>' . self::REQUIRED_FILENAME . '</code>'
+				)
+			);
+		}
+
+		if ( ! is_readable( $file ) ) {
+			return new WP_Error(
+				'resource_file_unreadable',
+				__( 'The file could not be read.', 'wporg-plugins' ),
+				array(
+					'file' => $file,
+				)
+			);
+		}
+
+		$content = file_get_contents( $file );
+
+		if ( false === $content ) {
+			return new WP_Error(
+				'resource_file_failed_retrieval',
+				__( 'Could not get the contents of the file.', 'wporg-plugins' ),
+				array(
+					'file' => $file,
+				)
+			);
+		}
+
+		return $content;
+	}
+
+	/**
+	 * Parse a JSON string into an object, and handle parsing errors.
+	 *
+	 * @param string $content
+	 *
+	 * @return object|WP_Error
+	 */
+	protected static function parse_content( $content ) {
+		$parsed = json_decode( $content );
+		$error  = json_last_error_msg();
+
+		// TODO Once we are on PHP 7.3 we can use the JSON_THROW_ON_ERROR option and catch an exception here.
+		if ( 'No error' !== $error ) {
+			return new WP_Error(
+				'json_parse_error',
+				sprintf(
+					__( 'JSON Parser: %s', 'wporg-plugins' ),
+					esc_html( $error )
+				),
+				array(
+					'error_code' => json_last_error(),
+				)
+			);
+		}
+
+		return $parsed;
+	}
+}
diff --git a/block-json/class-validator.php b/block-json/class-validator.php
new file mode 100644
index 0000000..e9a8b88
--- /dev/null
+++ b/block-json/class-validator.php
@@ -0,0 +1,554 @@
+<?php
+
+namespace WordPressdotorg\Plugin_Directory\Block_JSON;
+
+use WP_Error;
+
+defined( 'WPINC' ) || die();
+
+/**
+ * Class Validator
+ *
+ * @package WordPressdotorg\Plugin_Directory\Block_JSON
+ */
+class Validator {
+	/**
+	 * @var WP_Error
+	 */
+	protected $messages;
+
+	/**
+	 * Validator constructor.
+	 */
+	public function __construct() {
+		$this->messages = new WP_Error();
+	}
+
+	/**
+	 * The schema for the block.json file.
+	 *
+	 * This attempts to follow the schema for the schema.
+	 * See https://json-schema.org/understanding-json-schema/reference/index.html
+	 *
+	 * @return array
+	 */
+	public static function schema() {
+		return array(
+			'type'                 => 'object',
+			'properties'           => array(
+				'attributes'   => array(
+					'type'                 => 'object',
+					'additionalProperties' => array(
+						'type'       => 'object',
+						'properties' => array(
+							'attribute' => array(
+								'type' => 'string',
+							),
+							'meta'      => array(
+								'type' => 'string',
+							),
+							'multiline' => array(
+								'type' => 'string',
+							),
+							'query'     => array(
+								'type' => 'object',
+							),
+							'selector'  => array(
+								'type' => 'string',
+							),
+							'source'    => array(
+								'type' => 'string',
+								'enum' => array( 'attribute', 'text', 'html', 'query' ),
+							),
+							'type'      => array(
+								'type' => 'string',
+								'enum' => array( 'null', 'boolean', 'object', 'array', 'number', 'string', 'integer' ),
+							),
+						),
+						'required'   => array( 'type' ),
+					),
+				),
+				'category'     => array(
+					'type' => 'string',
+				),
+				'comment'      => array(
+					'type' => 'string',
+				),
+				'description'  => array(
+					'type' => 'string',
+				),
+				'editorScript' => array(
+					'type'    => 'string',
+					'pattern' => '\.js$',
+				),
+				'editorStyle'  => array(
+					'type'    => 'string',
+					'pattern' => '\.css$',
+				),
+				'example'      => array(
+					'type'                 => 'object',
+					'additionalProperties' => array(
+						'type' => 'object',
+					),
+				),
+				'icon'         => array(
+					'type' => 'string',
+				),
+				'keywords'     => array(
+					'type'  => 'array',
+					'items' => array(
+						'type' => 'string',
+					),
+				),
+				'name'         => array(
+					'type' => 'string',
+				),
+				'parent'       => array(
+					'type'  => 'array',
+					'items' => array(
+						'type' => 'string',
+					),
+				),
+				'script'       => array(
+					'type'    => 'string',
+					'pattern' => '\.js$',
+				),
+				'style'        => array(
+					'type'    => 'string',
+					'pattern' => '\.css$',
+				),
+				'styles'       => array(
+					'type'  => 'array',
+					'items' => array(
+						'type'       => 'object',
+						'properties' => array(
+							'isDefault' => array(
+								'type' => 'boolean',
+							),
+							'label'     => array(
+								'type' => 'string',
+							),
+							'name'      => array(
+								'type' => 'string',
+							),
+						),
+					),
+				),
+				'supports'     => array(
+					'type'       => 'object',
+					'properties' => array(
+						'align'           => array(
+							'type'  => array( 'boolean', 'array' ),
+							'items' => array(
+								'type' => 'string',
+								'enum' => array( 'left', 'center', 'right', 'wide', 'full' ),
+							),
+						),
+						'alignWide'       => array(
+							'type' => 'boolean',
+						),
+						'anchor'          => array(
+							'type' => 'boolean',
+						),
+						'className'       => array(
+							'type' => 'boolean',
+						),
+						'customClassName' => array(
+							'type' => 'boolean',
+						),
+						'html'            => array(
+							'type' => 'boolean',
+						),
+						'inserter'        => array(
+							'type' => 'boolean',
+						),
+						'multiple'        => array(
+							'type' => 'boolean',
+						),
+						'reusable'        => array(
+							'type' => 'boolean',
+						),
+					),
+				),
+				'textdomain'   => array(
+					'type' => 'string',
+				),
+				'title'        => array(
+					'type' => 'string',
+				),
+			),
+			'required'             => array( 'name', 'title' ),
+			'additionalProperties' => false,
+		);
+	}
+
+	/**
+	 * Validate a PHP object representation of a block.json file.
+	 *
+	 * @param object|WP_Error $block_json
+	 *
+	 * @return bool|WP_Error
+	 */
+	public function validate( $block_json ) {
+		// A WP_Error instance is technically an object, but shouldn't be validated.
+		if ( is_wp_error( $block_json ) ) {
+			return $block_json;
+		}
+
+		$schema = self::schema();
+
+		$this->validate_object( $block_json, 'block.json', $schema );
+		$this->check_conditional_properties( $block_json );
+
+		if ( $this->messages->has_errors() ) {
+			return $this->messages;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Check for properties that are conditionally required.
+	 *
+	 * @param object $block_json
+	 *
+	 * @return void
+	 */
+	protected function check_conditional_properties( $block_json ) {
+		if ( ! is_object( $block_json ) ) {
+			return;
+		}
+
+		if ( ! isset( $block_json->script ) && ! isset( $block_json->editorScript ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'At least one of the following properties must be present: %s', 'wporg-plugins' ),
+					// translators: used between list items, there is a space after the comma.
+					'<code>script</code>' . __( ', ', 'wporg-plugins' ) . '<code>editorScript</code>'
+				)
+			);
+			$this->append_error_data( 'block.json:script', 'error' );
+			$this->append_error_data( 'block.json:editorScript', 'error' );
+		}
+
+		if ( ! isset( $block_json->style ) && ! isset( $block_json->editorStyle ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'At least one of the following properties must be present: %s', 'wporg-plugins' ),
+					// translators: used between list items, there is a space after the comma.
+					'<code>style</code>' . __( ', ', 'wporg-plugins' ) . '<code>editorStyle</code>'
+				)
+			);
+			$this->append_error_data( 'block.json:style', 'error' );
+			$this->append_error_data( 'block.json:editorStyle', 'error' );
+		}
+	}
+
+	/**
+	 * Validate an object and its properties.
+	 *
+	 * @param object $object The value to validate as an object.
+	 * @param string $prop   The name of the property, used in error reporting.
+	 * @param array  $schema The schema for the property, used for validation.
+	 *
+	 * @return bool
+	 */
+	protected function validate_object( $object, $prop, $schema ) {
+		if ( ! is_object( $object ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'The %s property must contain an object value.', 'wporg-plugins' ),
+					'<code>' . $prop . '</code>'
+				)
+			);
+			$this->append_error_data( $prop, 'error' );
+
+			return false;
+		}
+
+		$results = array();
+
+		if ( isset( $schema['required'] ) ) {
+			foreach ( $schema['required'] as $required_prop ) {
+				if ( ! property_exists( $object, $required_prop ) ) {
+					$this->messages->add(
+						'error',
+						sprintf(
+							__( 'The %1$s property is required in the %2$s object.', 'wporg-plugins' ),
+							'<code>' . $required_prop . '</code>',
+							'<code>' . $prop . '</code>'
+						)
+					);
+					$this->append_error_data( "$prop:$required_prop", 'error' );
+					$results[] = false;
+				}
+			}
+		}
+
+		if ( isset( $schema['properties'] ) ) {
+			foreach ( $schema['properties'] as $subprop => $subschema ) {
+				if ( ! isset( $object->$subprop ) ) {
+					continue;
+				}
+
+				if ( isset( $subschema['type'] ) ) {
+					$results[] = $this->route_validation_for_type(
+						$subschema['type'],
+						$object->$subprop,
+						"$prop:$subprop",
+						$subschema
+					);
+				}
+			}
+		}
+
+		if ( isset( $schema['additionalProperties'] ) ) {
+			if ( false === $schema['additionalProperties'] ) {
+				foreach ( array_keys( get_object_vars( $object ) ) as $key ) {
+					if ( ! isset( $schema['properties'][ $key ] ) ) {
+						$this->messages->add(
+							'warning',
+							sprintf(
+								__( '%1$s is not a valid property in the %2$s object.', 'wporg-plugins' ),
+								'<code>' . $key . '</code>',
+								'<code>' . $prop . '</code>'
+							)
+						);
+						$this->append_error_data( "$prop:$key", 'warning' );
+						$results[] = false;
+						continue;
+					}
+				}
+			} elseif ( isset( $schema['additionalProperties']['type'] ) ) {
+				foreach ( $object as $subprop => $subvalue ) {
+					$results[] = $this->route_validation_for_type(
+						$schema['additionalProperties']['type'],
+						$subvalue,
+						"$prop:$subprop",
+						$schema['additionalProperties']
+					);
+				}
+			}
+		}
+
+		return ! in_array( false, $results, true );
+	}
+
+	/**
+	 * Validate an array and its items.
+	 *
+	 * @param array  $array  The value to validate as an array.
+	 * @param string $prop   The name of the property, used in error reporting.
+	 * @param array  $schema The schema for the property, used for validation.
+	 *
+	 * @return bool
+	 */
+	protected function validate_array( $array, $prop, $schema ) {
+		if ( ! is_array( $array ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'The %s property must contain an array value.', 'wporg-plugins' ),
+					'<code>' . $prop . '</code>'
+				)
+			);
+			$this->append_error_data( $prop, 'error' );
+
+			return false;
+		}
+
+		if ( isset( $schema['items']['type'] ) ) {
+			$results = array();
+			$index   = 0;
+
+			foreach ( $array as $item ) {
+				$results[] = $this->route_validation_for_type(
+					$schema['items']['type'],
+					$item,
+					$prop . "[$index]",
+					$schema['items']
+				);
+				$index ++;
+			}
+
+			return ! in_array( false, $results, true );
+		}
+
+		return true;
+	}
+
+	/**
+	 * Validate a string.
+	 *
+	 * @param string $string The value to validate as a string.
+	 * @param string $prop   The name of the property, used in error reporting.
+	 * @param array  $schema The schema for the property, used for validation.
+	 *
+	 * @return bool
+	 */
+	protected function validate_string( $string, $prop, $schema ) {
+		if ( ! is_string( $string ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'The %s property must contain a string value.', 'wporg-plugins' ),
+					'<code>' . $prop . '</code>'
+				)
+			);
+			$this->append_error_data( $prop, 'error' );
+
+			return false;
+		}
+
+		if ( isset( $schema['enum'] ) ) {
+			if ( ! in_array( $string, $schema['enum'], true ) ) {
+				$this->messages->add(
+					'warning',
+					sprintf(
+						__( '"%1$s" is not a valid value for the %2$s property.', 'wporg-plugins' ),
+						esc_html( $string ),
+						'<code>' . $prop . '</code>'
+					)
+				);
+				$this->append_error_data( $prop, 'warning' );
+			}
+		}
+
+		if ( isset( $schema['pattern'] ) ) {
+			if ( ! preg_match( '#' . $schema['pattern'] . '#', $string ) ) {
+				$pattern_description = $this->get_human_readable_pattern_description( $schema['pattern'] );
+				if ( $pattern_description ) {
+					$message = sprintf(
+						$pattern_description,
+						'<code>' . $prop . '</code>'
+					);
+				} else {
+					$message = sprintf(
+						__( 'The value of %s does not match the required pattern.', 'wporg-plugins' ),
+						'<code>' . $prop . '</code>'
+					);
+				}
+
+				$this->messages->add( 'warning', $message );
+				$this->append_error_data( $prop, 'warning' );
+			}
+		}
+
+		return true;
+	}
+
+	/**
+	 * Validate a boolean.
+	 *
+	 * @param bool   $boolean The value to validate as a boolean.
+	 * @param string $prop    The name of the property, used in error reporting.
+	 *
+	 * @return bool
+	 */
+	protected function validate_boolean( $boolean, $prop ) {
+		if ( ! is_bool( $boolean ) ) {
+			$this->messages->add(
+				'error',
+				sprintf(
+					__( 'The %s property must contain a boolean value.', 'wporg-plugins' ),
+					'<code>' . $prop . '</code>'
+				)
+			);
+			$this->append_error_data( $prop, 'error' );
+
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Send a property value to the correct validator depending on which type(s) it can be.
+	 *
+	 * @param string|array $valid_types
+	 * @param mixed        $value
+	 * @param string       $prop
+	 * @param array        $schema
+	 *
+	 * @return bool
+	 */
+	protected function route_validation_for_type( $valid_types, $value, $prop, $schema ) {
+		// There is a single valid type.
+		if ( is_string( $valid_types ) ) {
+			$method = "validate_$valid_types";
+			return $this->$method( $value, $prop, $schema );
+		}
+
+		// There are multiple valid types in an array.
+		foreach ( $valid_types as $type ) {
+			switch ( $type ) {
+				case 'boolean':
+					$check = 'is_bool';
+					break;
+				default:
+					$check = "is_$type";
+					break;
+			}
+
+			if ( $check( $value ) ) {
+				$method = "validate_$type";
+				return $this->$method( $value, $prop, $schema );
+			}
+		}
+
+		// Made it this far, it's none of the valid types.
+		$this->messages->add(
+			'error',
+			sprintf(
+				__( 'The %1$s property must contain a value that is one of these types: %2$s', 'wporg-plugins' ),
+				'<code>' . $prop . '</code>',
+				// translators: used between list items, there is a space after the comma.
+				'<code>' . implode( '</code>' . __( ', ', 'wporg-plugins' ) . '<code>', $valid_types ) . '</code>'
+			)
+		);
+		$this->append_error_data( $prop, 'error' );
+
+		return false;
+	}
+
+	/**
+	 * Add more data to an error code.
+	 *
+	 * The `add_data` method in WP_Error replaces data with each subsequent call with the same error code.
+	 *
+	 * @param mixed  $new_data   The data to append.
+	 * @param string $error_code The error code to assign the data to.
+	 *
+	 * @return void
+	 */
+	protected function append_error_data( $new_data, $error_code ) {
+		$data   = $this->messages->get_error_data( $error_code ) ?: array();
+		$data[] = $new_data;
+		$this->messages->add_data( $data, $error_code );
+	}
+
+	/**
+	 * Get a description of a regex pattern that can be understood by humans.
+	 *
+	 * @param string $pattern A regex pattern.
+	 *
+	 * @return string
+	 */
+	protected function get_human_readable_pattern_description( $pattern ) {
+		$description = '';
+
+		switch ( $pattern ) {
+			case '\.css$':
+				$description = __( 'The value of %s must end in ".css".', 'wporg-plugins' );
+				break;
+			case '\.js$':
+				$description = __( 'The value of %s must end in ".js".', 'wporg-plugins' );
+				break;
+		}
+
+		return $description;
+	}
+}
diff --git a/cli/class-import.php b/cli/class-import.php
index 810eae9..b7b34fa 100644
--- a/cli/class-import.php
+++ b/cli/class-import.php
@@ -4,6 +4,7 @@
 use Exception;
 use WordPressdotorg\Plugin_Directory\Jobs\API_Update_Updater;
 use WordPressdotorg\Plugin_Directory\Jobs\Tide_Sync;
+use WordPressdotorg\Plugin_Directory\Block_JSON;
 use WordPressdotorg\Plugin_Directory\Plugin_Directory;
 use WordPressdotorg\Plugin_Directory\Readme\Parser;
 use WordPressdotorg\Plugin_Directory\Template;
@@ -658,10 +659,26 @@ static function find_blocks_in_file( $filename ) {
 			}
 		}
 		if ( 'block.json' === basename( $filename ) ) {
-			// A block.json file has everything we want.
-			$blockinfo = json_decode( file_get_contents( $filename ) );
-			if ( isset( $blockinfo->name ) ) {
-				$blocks[] = $blockinfo;
+			// A block.json file should have everything we want.
+			$validator = new Block_JSON\Validator();
+			$block     = Block_JSON\Parser::parse( array( 'file' => $filename ) );
+			$result    = $validator->validate( $block );
+			if ( ! is_wp_error( $block ) && is_wp_error( $result ) ) {
+				// Only certain properties must be valid for our purposes here.
+				$required_valid_props = array(
+					'block.json',
+					'block.json:editorScript',
+					'block.json:editorStyle',
+					'block.json:name',
+					'block.json:script',
+					'block.json:style',
+				);
+				$invalid_props = array_intersect( $required_valid_props, $result->get_error_data( 'error' ) );
+				if ( empty( $invalid_props ) ) {
+					$blocks[] = $block;
+				}
+			} elseif ( true === $result ) {
+				$blocks[] = $block;
 			}
 		}