wp-includes/link-template.php:4219Injects rel=shortlink into the head if a shortlink is defined for the current page.
function wp_shortlink_wp_head() { $shortlink = wp_get_shortlink( 0, 'query' ); if ( empty( $shortlink ) ) { return; } echo "<link rel='shortlink' href='" . esc_url( $shortlink ) . "' />\n";}Introduced in 3.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/link-template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.