What does `theme_support` do when added via `add_theme_support()`?

Question

WordPress Fundamental — Medium

What does `theme_support` do when added via `add_theme_support()`?

Accepted Answer

Adding `theme_support` via `add_theme_support()` declares that the theme supports specific WordPress features like post-thumbnails, menus, HTML5 markup, and custom headers. This function does not register the theme for automatic updates, enable support tickets, or add the theme to the supported browsers compatibility list.