WordPress at a glance
filter is not described

rest_url_prefix filter-hook . WP 4.4.0

Filters the REST URL prefix.

Usage

add_filter( 'rest_url_prefix', 'filter_function_name_1732' );
function filter_function_name_1732( $prefix ){
	// filter...

	return $prefix;
}
$prefix(string)
URL prefix.
Default: 'wp-json'

Where the hook is called

rest_get_url_prefix()
wp-includes/rest-api.php 316
return apply_filters( 'rest_url_prefix', 'wp-json' );

Where the hook is used (in WP core)

Does not used.