// Add WebP MIME type support

function add_webp_mime_type($mime_types) {

    $mime_types['webp'] = 'image/webp';

    return $mime_types;

}

add_filter('upload_mimes', 'add_webp_mime_type');

// Enable WebP in the Media Library

function enable_webp_upload($data, $file) {

    $file['ext'] = 'webp';

    return $data;

}

add_filter('wp_handle_upload_prefilter', 'enable_webp_upload', 10, 2);

// Enable WebP thumbnails

function display_webp_media($result, $path) {

    if ($result === false) {

        $info = pathinfo($path);

        $ext = $info['extension'];

        if ($ext === 'webp') {

            return array('ext' => 'jpg', 'mime-type' => 'image/jpeg');

        }

    }

    return $result;

}

add_filter('file_is_displayable_image', 'display_webp_media', 10, 2);