Drupal core themes

The four Drupal 8 core themes live inside the core/themes folder. As part of the Drupal 8 Mobile Initiative all of Drupal core's themes have been converted to a responsive design. All of the core theme (not base themes) must function when used as an administration theme. Since Drupal 8 is multilingual, the core themes must also support bidirectional text.

NOTE: Stark had a stylesheet inside the theme to make sure the regions were responsive. However, this stylesheet got removed. Read more on this in the Stark section.

• bartik: A flexible, recolorable theme with many regions and a responsive, mobile-first layout.
• seven: The default administration theme for Drupal 8 was designed with clean lines, simple blocks, and sans-serif font to emphasize the tools and tasks at hand.
• stark: An intentionally plain theme with almost no styling to demonstrate default Drupal’s HTML and CSS.

You might remember these three themes from Drupal 7. But wait, there's more ...

• classy: [meta] Results of Drupalcon Austin's Consensus Banana: At DrupalCon Austin (2014) the need for a new core theme came up. Classy is a base theme that Seven and Bartik will extend from.
• stable: The Stable theme will function as a backwards compatibility layer for Drupal 8's core markup, CSS and JS. A theme will use Stable as the base theme if no base theme is set in its .info.yml file.

Here's an overview of the Drupal 8 core themes and how they relate to each other.