WordPress at a glance
filter is not described

the_excerpt filter-hook . WP 1.0

This filter is documented in wp-includes/post-template.php

Usage

add_filter( 'the_excerpt', 'filter_function_name_249' );
function filter_function_name_249( $excerpt ){
	// filter...

	return $excerpt;
}
$excerpt
-

Where the hook is called

WP_REST_Posts_Controller::prepare_item_for_response()
the_excerpt
WP_REST_Revisions_Controller::prepare_excerpt_response()
the_excerpt
WP_REST_Attachments_Controller::prepare_item_for_response()
the_excerpt
the_excerpt()
the_excerpt
do_trackbacks()
the_excerpt
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 1697
$excerpt = apply_filters( 'the_excerpt', $excerpt );
wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php 826
$excerpt = apply_filters( 'the_excerpt', $excerpt, $post );
wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php 698
$caption = apply_filters( 'the_excerpt', $caption );
wp-includes/post-template.php 394
echo apply_filters( 'the_excerpt', get_the_excerpt() );
wp-includes/comment.php 2887
$excerpt = apply_filters( 'the_excerpt', $post->post_excerpt );

Where in WP core the hook is used WordPress

wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 180
add_filter( 'the_excerpt', 'wptexturize' );
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 181
add_filter( 'the_excerpt', 'convert_smilies' );
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 182
add_filter( 'the_excerpt', 'convert_chars' );
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 184
add_filter( 'the_excerpt', 'shortcode_unautop' );
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php 185
add_filter( 'the_excerpt', 'wp_filter_content_tags' );