diff --git a/activitypub.php b/activitypub.php
index b347814..6ae9dbc 100644
--- a/activitypub.php
+++ b/activitypub.php
@@ -19,6 +19,7 @@ namespace Activitypub;
  * Initialize plugin
  */
 function init() {
+	\defined( 'ACTIVITYPUB_EXCERPT_LENGTH' ) || \define( 'ACTIVITYPUB_EXCERPT_LENGTH', 400 );
 	\defined( 'ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS' ) || \define( 'ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS', 3 );
 	\defined( 'ACTIVITYPUB_HASHTAGS_REGEXP' ) || \define( 'ACTIVITYPUB_HASHTAGS_REGEXP', '(?:(?<=\s)|(?<=<p>)|(?<=<br>)|^)#([A-Za-z0-9_]+)(?:(?=\s|[[:punct:]]|$))' );
 	\defined( 'ACTIVITYPUB_ALLOWED_HTML' ) || \define( 'ACTIVITYPUB_ALLOWED_HTML', '<strong><a><p><ul><ol><li><code><blockquote><pre><img>' );
diff --git a/includes/model/class-post.php b/includes/model/class-post.php
index a062829..f9bde0d 100644
--- a/includes/model/class-post.php
+++ b/includes/model/class-post.php
@@ -242,7 +242,15 @@ class Post {
 
 				break;
 			case 'ap_excerpt':
-				echo $this->get_the_post_excerpt();
+				$length = ACTIVITYPUB_EXCERPT_LENGTH;
+
+				if( is_array( $atts ) && array_key_exists( 'length', $atts ) ) {
+					$length = intval( $atts['length'] );
+				}
+
+				if( $length == 0 ) { $length = ACTIVITYPUB_EXCERPT_LENGTH; }
+
+				echo $this->get_the_post_excerpt( $length );
 
 				break;
 			case 'ap_content':
@@ -370,7 +378,7 @@ class Post {
 	 *
 	 * @return string The excerpt.
 	 */
-	public function get_the_post_excerpt( $excerpt_length = 400 ) {
+	public function get_the_post_excerpt( $excerpt_length = ACTIVITYPUB_EXCERPT_LENGTH ) {
 		$post = $this->post;
 
 		$excerpt = \get_post_field( 'post_excerpt', $post );
diff --git a/templates/settings.php b/templates/settings.php
index e8d6529..23242ae 100644
--- a/templates/settings.php
+++ b/templates/settings.php
@@ -62,14 +62,16 @@ $thumnail_size = $image_sizes['thumbnail']['width'] . 'x' . $image_sizes['thumbn
 							<details>
 								<summary><?php esc_html_e( 'See the complete list of activitypub shortcodes.', 'activitypub' ); ?></summary>
 								<div class="description">
+									<p><?php esc_html_e( 'You may use any shortcode normally available to you on your site, however be aware that shortcodes may significantly increase the size of your content depending on what they do. '); ?>
+									<p><?php esc_html_e( 'In addition, the following shortcodes are available during an activitypub post:'); ?>
 									<ul>
-										<li><code>[ap_title]</code> - <?php \esc_html_e( 'The Post-Title.', 'activitypub' ); ?></li>
-										<li><code>[ap_content]</code> - <?php \esc_html_e( 'The Post-Content.', 'activitypub' ); ?></li>
-										<li><code>[ap_excerpt]</code> - <?php \esc_html_e( 'The Post-Excerpt (default 400 Chars).', 'activitypub' ); ?></li>
-										<li><code>[ap_permalink]</code> - <?php \esc_html_e( 'The Post-Permalink.', 'activitypub' ); ?></li>
+										<li><code>[ap_title]</code> - <?php \esc_html_e( 'The post\'s title.', 'activitypub' ); ?></li>
+										<li><code>[ap_content]</code> - <?php \esc_html_e( 'The post\'s content.', 'activitypub' ); ?></li>
+										<li><code>[ap_excerpt <i>lenght=nnn</i>]</code> - <?php \esc_html_e( 'The post\'s excerpt (default 400 chars). length parameter is optional.', 'activitypub' ); ?></li>
+										<li><code>[ap_permalink]</code> - <?php \esc_html_e( 'The post\'s permalink.', 'activitypub' ); ?></li>
 										<?php // translators: ?>
-										<li><code>[ap_shortlink]</code> - <?php echo \wp_kses( \__( 'The Post-Shortlink. I can recommend <a href="https://wordpress.org/plugins/hum/" target="_blank">Hum</a>, to prettify the Shortlinks', 'activitypub' ), 'default' ); ?></li>
-										<li><code>[ap_hashtags]</code> - <?php \esc_html_e( 'The Tags as Hashtags.', 'activitypub' ); ?></li>
+										<li><code>[ap_shortlink]</code> - <?php echo \wp_kses( \__( 'The post\'s shortlink. I can recommend <a href="https://wordpress.org/plugins/hum/" target="_blank">Hum</a>, to prettify the Shortlinks', 'activitypub' ), 'default' ); ?></li>
+										<li><code>[ap_hashtags]</code> - <?php \esc_html_e( 'The post\'s tags as hashtags.', 'activitypub' ); ?></li>
 										<li><code>[ap_hashcats]</code> - <?php \esc_html_e( 'The post\'s categories as hashtags.', 'activitypub' ); ?></li>
 										<li><code>[ap_image]</code> - <?php \esc_html_e( 'The URL for the post\'s featured image, full size.', 'activitypub' ); ?></li>
 										<li><code>[ap_thumbnail]</code> - <?php echo \wp_kses( sprintf( __( 'The URL for the post\'s featured image thumbnail size (%s).', 'activitypub'), $thumnail_size ), 'default' ); ?></li>