Custom Module Development in Drupal 9

Step 1: Name the Drupal 9 Module:

1. This is the first step to create a module under ‘web/modules/custom’ folder. We will name that module as first_module.

Step 2: Create an info file:

1. Under the first_module folder we will create a info.yml file starting from the machine name. In our case it will be "first_module.info.yml".

Step 3: Install:

1. Under the route "/admin/modules", we can find our first module and install that.