.. tip::

    To apply a tag to all your autoconfigured services extending a class or an
    interface, call ``ContainerBuilder::registerForAutoconfiguration()`` in an
    :doc:`extension </bundles/extension>` or from your kernel::

        // app/AppKernel.php
        class AppKernel extends Kernel
        {
            // ...

            protected function build(ContainerBuilder $container)
            {
                $container->registerForAutoconfiguration(CustomInterface::class)
                    ->addTag('app.custom_tag')
                ;
            }
        }