Source

File: wp-includes/class-wp-rewrite.php

public function page_rewrite_rules() {
		// The extra .? at the beginning prevents clashes with other regular expressions in the rules array.
		$this->add_rewrite_tag( '%pagename%', '(.?.+?)', 'pagename=' );

		return $this->generate_rewrite_rules( $this->get_page_permastruct(), EP_PAGES, true, true, false, false );
	}