How to customize a WordPress theme’s design and layout

Create a backup or work on a staging copy before changing templates, CSS or theme files. A design change can affect every page, and a mistake in a template or stylesheet can make the front end look broken.

Check whether the active theme is a block theme or a classic theme. Block themes normally use Appearance → Editor, while classic themes commonly provide Appearance → Customize. The Customizer is hidden for many block themes, so do not assume it is missing because WordPress is malfunctioning.

For a block theme, open Appearance → Editor → Styles and set the site-wide colours, typography, layout widths, spacing and element styles. For a classic theme, open Appearance → Customize and use the theme's available controls for identity, colours, menus, widgets and homepage settings.

Save or publish the changes only after checking the preview. Global styles are the right place for site-wide changes; editing individual pages first often creates inconsistent headings, buttons and spacing.

Use the Site Editor's Templates, Template parts and Patterns to change the layout of headers, footers, single posts, pages, archives and other repeated areas. Edit a template when the change should appear across many pages; edit a page or pattern when it is specific to one area.

With a classic theme, use the theme's layout settings, widgets, menus and page builder controls where available. Do not edit the parent theme's PHP files directly unless you are prepared to repeat the work after a theme update. Child themes can override parent templates and parts while keeping the parent theme available for updates.

Use the block theme's Styles area or the classic theme's Additional CSS panel for limited visual changes such as a colour, border, font size or extra spacing. Give the rule a clear scope so it does not unexpectedly change every button, heading or link on the site.

If you need substantial CSS, template overrides or custom functionality, create and activate a child theme. A child theme is safer than editing the parent theme, but its stylesheet must actually be loaded and may need selectors with enough specificity to override the parent styles. Never rely on !important as the first fix.

Review the homepage, navigation, content templates, forms and checkout on desktop, tablet and phone widths. Look for text wrapping, horizontal scrolling, clipped images, oversized headings, buttons that are hard to tap and headers that cover content. Divi and some other themes provide separate responsive values for devices, but you still need to inspect the finished pages rather than trusting the editor preview.

If the change is not visible, clear the browser, page-cache, server, CDN and theme-generated CSS caches. Then inspect the element in browser developer tools: confirm the stylesheet loads, check which rule wins, and verify that the selector matches the current markup. Cache and specificity problems are frequent reasons CSS appears not to work.

The quickest route is the theme's own visual builder or design system. If the site uses Divi, edit the page with the Visual Builder, change the section, row or module settings, and use the Theme Builder for reusable headers, footers, post layouts and archive layouts. Divi also supports responsive values, per-element CSS and site-wide CSS controls.

For deeper Divi-specific work, the Divi Booster Plugin for WordPress can be a practical shortcut because it adds extra CSS and JavaScript controls, responsive settings, header and footer tools, layout options and performance-related controls. Choose it only for a Divi site; it does not replace the Site Editor or Customizer for unrelated themes.