HTML Attributes Customizer for Blocks

No. The editor shows raw {{…}} tokens; replacement runs on the published front end.

Yes. Register a token in the editor reference, resolve it on the front end, then use it in attribute values as {{my.plugin.token}}. 1. Register the token (shows in the Variables tab): add_filter( 'htmlbac_variable_definitions', function ( $definitions ) { $definitions[] = array( 'key' => 'my.plugin.token', 'group' => 'other', 'description' => __( 'Example custom token for HTML attributes.', 'my-plugin' ), ); return $definitions; } ); 2. Resolve the token when the block renders: add_filter( 'htmlbac_resolve_variable', function ( $value, $key ) { if ( 'my.plugin.token' === $key ) { return esc_attr( 'hello-from-my-plugin' ); } return $value; }, 10, 2 ); 3. Optional — override the full replacement map in one place: add_filter( 'htmlbac_variable_replacements', function ( $replacements ) { $replacements['my.plugin.token'] = esc_attr( 'hello-from-my-plugin' ); return $replacements; } ); In the block sidebar, add a line such as data-example="{{my.plugin.token}}".

Blocks such as Group, Image, and Video output an inner div, img, or video that the outer wrapper cannot target. Use Inner element for those. Enable inner attributes for more blocks (built-in strategies): Built-in strategy keys include group_inner, first_img, first_video, first_a, first_figure, and others. Map a block name to one of those keys: add_filter( 'htmlbac_inner_target_blocks', function ( $strategies ) { $strategies['core/cover'] = 'first_img'; $strategies['core/button'] = 'first_a'; return $strategies; } ); Custom strategy (when no built-in key fits): add_filter( 'htmlbac_inner_target_blocks', function ( $strategies ) { $strategies['my-plugin/my-block'] = 'my_first_button'; return $strategies; } ); add_filter( 'htmlbac_apply_inner_strategy', function ( $block_content, $entries, $strategy, $block_name ) { if ( 'my_first_button' !== $strategy || 'my-plugin/my-block' !== $block_name ) { return $block_content; } if ( ! class_exists( 'WP_HTML_Tag_Processor' ) ) { return $block_content; } $processor = new WP_HTML_Tag_Processor( $block_content ); if ( ! $processor->next_tag( 'button' ) ) { return $block_content; } foreach ( $entries as $entry ) { $name = isset( $entry['name'] ) ? (string) $entry['name'] : ''; if ( '' === $name ) { continue; } if ( null === $entry['value'] ) { $processor->set_attribute( $name, true ); continue; } $processor->set_attribute( $name, (string) $entry['value'] ); } return $processor->get_updated_html(); }, 10, 4 );