wp-includes/post-thumbnail-template.php:281Displays the post thumbnail URL.
$sizestring|int[]optional'post-thumbnail'function the_post_thumbnail_url( $size = 'post-thumbnail' ) { $url = get_the_post_thumbnail_url( null, $size ); if ( $url ) { echo esc_url( $url ); }}Introduced in 4.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/post-thumbnail-template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.