/themes directory

The /themes directory is mapped to /wp-content/themes/ ; this directory works similarly to WP_CONTENT_DIR . '/themes/' in a self-hosted WordPress installation.

Theme files and directories can only be added, removed, or updated via code commits to GitHub; not from within the WordPress Admin dashboard.

Code quality of a theme can be verified before adding it to a GitHub repository by scanning the theme code with PHP_Codesniffer (PHPCS). The scan will provide feedback on warnings and errors that exist within the theme’s code. Feedback from the scan should be reviewed, and acted on, including the possibility of seeking out a similar theme with higher code quality in some cases.

WordPress.org’s Theme Handbook is the best resource for answers to all theme-related questions. The Theme Handbook provides guidance for topics such as developing a custom theme, creating a child theme, and theme security best practices.

The Underscores (_s) base theme

The Underscores project is a basic starter theme intended for developing custom themes. It is a lean theme built with well-commented code, HTML5 templates, minimal CSS, and a variety of tools to help customize a theme.