How to create a child theme — One Line in style.css Does All the Inheriting

This assumes you can create files over SFTP or in File Manager and read a PHP function without flinching. It is short because the mechanism is short — the length in most tutorials comes from ceremony, not necessity.

It also says where a child theme is the wrong answer. On a block theme, most of what people build child themes for is now stored in the database and already survives updates.

Add a functions.php that hooks wp_enqueue_scripts and loads the parent stylesheet with wp_enqueue_style, using get_template_directory_uri() for the parent and get_stylesheet_directory_uri() for the child. Pass the theme version as the version argument so cache-busting follows your releases rather than a random query string.

The old @import approach still functions but serialises the two stylesheets: the browser must fetch and parse the child before it discovers it needs the parent. On a render-blocking resource that is a measurable delay to first paint, which is why it stopped being recommended.

On a block theme, full-site editing stores your customisations in the database, beyond the reach of an update. For colours, typography, templates and template parts, the site editor is now the right place and a child theme adds a directory for no benefit. Child themes remain correct for code: custom functions, hooks, template parts the editor cannot express.

If you are retrofitting one onto a parent that has already been edited directly, find those edits before the next update destroys them. Download a clean copy of the same parent version and diff it against the live folder — every change reveals itself in one pass, and SSH with Git on the developer plans makes that a two-minute job.