WordPress keeps surprising me even after more than a decade since I started using it.

Today I came to know that WordPress only generates canonical tags for singular pages (posts & pages). WordPress does not add canonical tags to archive pages including author page, post type archives, taxonomy archives etc.

So, how to add canonical tags to all archive pages? Use the wp_head action hook. Here is the script-

add_action( 'wp_head', 'add_canonical_url' );
function add_canonical_url() {
    if ( is_archive() ) {
        echo '<link rel="canonical" href="' . get_pagenum_link() . '" />';
    }
}