With this code, all attachment pages redirects to the frontpage. This is particularly helpful if you want to keep things tidy, or haven’t styled the attachment pages accordingly.
functions.php
function myprefix_redirect_attachment_page() {
if ( is_attachment() ) {
global $post;
if ( $post && $post->post_parent ) {
wp_redirect( esc_url( get_permalink( $post->post_parent ) ), 301 );
exit;
} else {
wp_redirect( esc_url( home_url( '/' ) ), 301 );
exit;
}
}
}
add_action( 'template_redirect', 'myprefix_redirect_attachment_page' );