For SEO, blindly redirecting every 404 to the homepage isn’t always recommended. A custom 404 page is often better.
/**
* Redirect frontend 404 pages to the homepage.
*/
function mytheme_redirect_404_to_home() {
if ( is_404() && ! is_admin() ) {
wp_safe_redirect( home_url( '/' ), 301 );
exit;
}
}
add_action( 'template_redirect', 'mytheme_redirect_404_to_home' );
