apply_filters( ‘admin_post_thumbnail_html’, string $content, int $post_id, int|null $thumbnail_id )

Filters the admin post thumbnail HTML markup to return.


Admin post thumbnail HTML markup.
Post ID.
Thumbnail attachment ID, or null if there isn’t one.


return apply_filters( 'admin_post_thumbnail_html', $content, $post->ID, $thumbnail_id );


4.6.0Added the $thumbnail_id parameter.
3.5.0Added the $post_id parameter.

User Contributed Notes

  1. Skip to note 3 content

    Below is an example of how to use this filter to provide some additional text to admins on what size image to use for their featured images. If an image is currently in place, this text will show above it. If not, the help text will show just above the “Set featured image” link.

    function filter_featured_image_admin_text( $content, $post_id, $thumbnail_id ){
        $help_text = '<p>' . __( 'Please use an image that is 1170 pixels wide x 658 pixels tall.', 'my_domain' ) . '</p>';
        return $help_text . $content;
    add_filter( 'admin_post_thumbnail_html', 'filter_featured_image_admin_text', 10, 3 );

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