Drupal 8 - How do I get the base path?

in this tuto, I'll show you how to get the base path in Drupal 8.

You can use url() to generate a base url to any route in Drupal. You can supply the <front> route which, in effect, will be your base URL.

in Twig use this :

{{ url('<front>') }}

in PHP files use this :

use Drupal\Core\Url;

$base_path = Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString();

Url::fromRoute() is used to create a new Url object for a URL that has a Drupal route.

Examples : 

// return https://codimth.com/node/72 for example

$path = Url::fromRoute('entity.node.canonical', ['node' => $id], ['absolute' => TRUE])->toString();

// return login link

$login_link = Url::fromRoute('user.login', [], ['absolute' => 'true'])->toString();