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Plugin API/Filter Reference/excerpt length

This filter is used by wp_trim_excerpt() function. By default the excerpt length is set to return 55 words.

To change excerpt length, add the following code to functions.php file in your theme:

function custom_excerpt_length( $length ) {
	return 20;
}
add_filter( 'excerpt_length', 'custom_excerpt_length', 999 );

Make sure to set the priority correctly, else the default WordPress filter on this function will run last and override what you set here.

wp_trim_excerpt() is located in wp-includes/formatting.php.