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filter is not described

document_title_separator filter-hook . WP 4.4.0

Filters the separator for the document title.

Usage

add_filter( 'document_title_separator', 'filter_function_name_7689' );
function filter_function_name_7689( $sep ){
	// filter...

	return $sep;
}
$sep(string)
Document title separator.
Default: '-'

Where the hook is called

wp_get_document_title()
wp-includes/general-template.php 1036
$sep = apply_filters( 'document_title_separator', '-' );

Where the hook is used (in WP core)

Does not used.