Twig templates for custom block types in Drupal

By default, a standard Drupal installation already comes with a predefined block type that is used when you add a custom block to a region: the Basic block. It only has a title and body field. Drupal block types work quite similar to content types. It allows you to create a particular type of block by adding and managing fields, form display and display modes.

Out of the box, Drupal offers several ways to use a Twig template to theme your custom block. However, when you want to create a Twig template that applies to all blocks of a specific block type, you need a few lines of code.

To enable templates for custom block types, we use theme suggestions. Assuming you have a custom Drupal theme called "mycustomtheme", place the following snippet in your mycustomtheme.theme file:

function mycustomtheme_theme_suggestions_block_alter(array &$suggestions, array $variables) 
{ 
  // Block suggestions for custom block types. 
  if (isset($variables['elements']['content']['#block_content'])) { 
    array_splice($suggestions, 1, 0, 'block__type__' . $variables['elements']['content']['#block_content']->bundle()); 
  } 
}

Now you can use block–type–my-block-type.html.twig to theme every custom block of the block type you have created.

Happy theming!