# Child theme: definition

> A child theme is a WordPress theme that inherits the appearance and functionality of a parent theme, while only overriding the files you actually want to customise.

- Source canonique : [https://allaux.fr/en/glossaire/theme-enfant](https://allaux.fr/en/glossaire/theme-enfant)
- Langue : EN
- Dernière mise à jour : 2026-09-30

## How it works alongside the parent theme

Technically, a child theme is a minimal folder containing at least a style.css file with a header stating Template: followed by the parent theme's folder name, and a functions.php file that loads the parent's stylesheet alongside its own. WordPress then merges the two: any file missing from the child is loaded from the parent, and any file present in the child takes precedence.

On a WooCommerce store, the benefit is immediate: customising a premium theme directly in its original files means those changes are lost the next time you click Update in wp-admin. A child theme isolates these changes in a separate folder, never touched by an update to the parent.

It's also the recommended way to override a WooCommerce template, but the copy path isn't symmetrical: the original file lives in the plugin, under wp-content/plugins/woocommerce/templates/, and has to be copied into wp-content/themes/my-child-theme/woocommerce/. The templates/ segment disappears along the way: templates/single-product/price.php becomes woocommerce/single-product/price.php. A file left inside a templates/ subfolder of the child theme is never loaded by WooCommerce, and the customisation has no effect.

## FAQ

### Does a child theme slow the site down?

Not noticeably: WordPress simply loads an extra stylesheet and a few extra files, which adds no significant weight compared to the parent theme alone.

### Can a child theme be created after the fact, once the site is already customised?

Yes, but you then need to manually carry over the customisations already made in the parent theme to the child theme, file by file.

### Does the child theme itself need updating?

It has no automatic update mechanism like a theme from the WordPress directory: its files change only if you edit them yourself or through the developer who maintains it.