How to Change or Customize Your WordPress Theme (and When to Use a Child Theme)

Your theme controls how your WordPress site looks: layout, colors, fonts, headers, and footers. You can switch themes, tweak the one you have, or use a child theme for deeper changes. These steps are for WordPress 6.x and later.

Block themes vs. classic themes

WordPress has two kinds of themes, and where you make changes depends on which one you have.

Block themes (like the default Twenty Twenty-Five) are customized in the Site Editor: Appearance > Editor.
Classic themes are usually customized in the Customizer: Appearance > Customize. Some classic themes and page builders have their own settings screens too.

If you see Editor under Appearance, you have a block theme. Depending on your version and theme, the Appearance menu may also list items like Patterns or Fonts.

Before you switch themes

Switching themes changes more than looks. Menus, widgets, and some page layouts may need to be set up again, and features built into the old theme can disappear.

Back up your site. See Website Backups: What to Back Up, How Often, and How Restores Work.
If you can, try the new theme on a staging (test) copy first.
Use Live Preview to see the new theme with your content before you activate it.

Install and activate a new theme

Go to Appearance > Themes.
Click Add Theme, search the directory, and click Install. For a theme you bought, click Upload Theme and choose the zip file.
On the theme's card, click Live Preview to check it.
Click Activate when you're happy. Your active theme's card shows Customize instead.
Check your menus, home page, and widgets or template parts, and fix anything that moved.

Customize the theme you have

Block theme:

Go to Appearance > Editor.
Click Styles to change colors, fonts, and spacing across the whole site.
Click Templates or Patterns to edit layouts, headers, and footers.
Click Save.

Classic theme:

Go to Appearance > Customize.
Work through the panels (they vary by theme). Changes show in the preview on the right.
Click Publish.

These changes are stored in your site's database, so normal theme updates won't wipe them out.

When you need a child theme

If you (or a developer) edit a theme's files directly, like its CSS, templates, or functions.php, those edits are lost the next time the theme updates. A child theme fixes that. It's a small theme that borrows everything from the main (parent) theme and holds only your changes. The parent theme can update safely while your changes stay put.

You probably need a child theme if:

You're adding custom code or editing theme template files
You're adding a lot of custom CSS

You probably don't need one if:

You only change settings in the Site Editor or Customizer
You only add a little CSS in Appearance > Customize > Additional CSS (classic themes) or the Additional CSS option in Styles (block themes)

How a child theme is set up

A child theme is a folder in wp-content/themes with at least a style.css file. The header at the top of that file names the parent theme in a Template: line. Classic child themes usually also have a functions.php file that loads the parent's styles. Some themes offer a ready-made child theme to download.

This is developer work, and a mistake can take your site down. Have someone comfortable with code set it up, and test it on a staging copy.

Keep your theme updated

Theme updates fix bugs and security issues just like plugin updates. Delete themes you don't use, but keep one default WordPress theme installed as a fallback. See How to Update WordPress Safely (Back Up First).

Prefer we handle it?

If you'd rather spend your time running your business, our boutique hosting, available to our clients, including sites moved over from another host, takes a proactive approach to security and monitoring, with nightly backups, 24/7 outage monitoring, and ongoing core CMS updates.

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