In this tutorial, we will take a look at Drupal's core base themes, with a focus on Stable and Classy.

There are five themes on Drupal 8 core:

• Bartik is the default user-facing theme
• Seven is the default administration theme
• Classy
• Stable
• Stark

Stark

Stark theme provides the absolute minimal amount of markup and CSS.

It's primarily for demonstration purposes, or for sites that have very strict markup and semantic requirements.

Stark probably isn't a good choice for a base theme.

But it can be incredibly helpful in tracking down module-related markup and CSS bugs.

Stable

Stable is Drupal's default "clean" base theme.

It provides minimal markup and a small handful of CSS classes.

When not use key base theme on info.yml file, Stable will be used.

The intent is that this Stable base theme will be used as a backwards compatibility layer protecting your theme against changes to core's markup and styling.

Classy

Classy provides the rich markup familiar to users of previous versions of Drupal.

Its markup provides many classes as well as an attempt at basic styling of core's markup.