It is always a little complicated to choose the most useful modules for Drupal 8 because it depends on the site you are going to create or administer. However, there are some handy modules that you can use in almost any situation.
I will tell you about the modules I use almost all the time in my Drupal 8 projects, they do not link to a particular type of site, but they are still used both in development and production.
1. Filter Module
The available modules’ page can become quite long and difficult to read when you have to manage large sites. To simplify the administration of the modules, you can install the Module Filter module. This module provides you with tabs for each package, giving you a new alternative to find and configure your modules faster.
This module will help you protect your development or staging site with HTTP authentication. Anonymous visitors and search engines will not be able to access your development site. But you and your customers can do it.
3. Environment Indicator
This module will allow you not to go crazy when working on several environments at once (dev, staging, prod) by adding a different (configurable) color to the main bar of each environment.
It’s handy when you have several environments, and you quickly forget which version you’re working on at a particular time. In general, I choose blue for the dev, green for staging and red for production.
4. Delete all
I always install this module locally and very often in development with the Devel Generate sub-module! The Delete All module allows you to remove all content or users from a site with a single click. You can also remove the content of a specific type of node.
This module is particularly useful on a test site that the client has used for a while and that we need to clean up before using real data or when we test the import of thousands of nodes. It is handy.
5. Admin Toolbar
The Admin Toolbar module will save you a lot of time. By having a drop-down menu and expanding the original Drupal menu, it will allow you to perform different tasks faster and easier.
This module works on the default toolbar module of the Drupal core, so it is a very light module, and it keeps all the features of the original module (shortcuts / responsive media).
This module comes with a sub-module called “Admin Toolbar Extra Tools” that adds additional links as did the Admin Menu module under Drupal 7 (flush caches, run cron, etc…).