What a WordPress customisable theme really means

You can customise every WordPress theme. The question is how far you can get without writing code, and whether your change will survive the next update. Most frustration with “customisable” themes comes from mixing up those two things.

This explainer covers what the word means in practice, how the two WordPress editing models differ, which layer each kind of change belongs in, and how to tell when a theme’s options have run out. If you are still choosing a base, our guide to layout and design on WordPress covers the structural side.

“Customisable” means options to an owner and code to a developer

For a developer who writes PHP, CSS and JavaScript, every theme is fully customisable. For an owner who doesn’t, “fully customisable” means the theme has a lot of built-in settings. Those are two very different promises, and theme marketing usually leaves you to work out which one you are getting.

The gap appears with very specific changes: the colour of the mobile menu, the spacing on one section, the font on a WooCommerce product page. A theme can have hundreds of settings and still not have the one you need. A WordPress.org support thread called “Editing a custom theme” shows how this goes. Someone took over an agency-built site and was installing plugins to make simple changes like padding, because the theme gave them no setting for it.

When you judge a theme, ignore how many options it has. Ask whether it lets you make the changes you will actually make, in a place that survives an update.

Which editor you have decides where the settings are

WordPress has two editing models. Most confusion about customisation starts when a tutorial describes one model and your site uses the other.

• Block themes are edited at Appearance > Editor, which opens the Site Editor. Styles (colours, typography, layout), templates and template parts such as the header and footer are all there. WordPress.org’s documentation says the Site Editor is only available when a block theme is active.
• Classic themes use Appearance > Customize, the Customizer, if the theme supports it. Many classic themes also add their own options page.

To check which one you have, open Appearance in the dashboard. If you see Editor, you have a block theme. If you see Customize, you have a classic theme. Some setups show both, either a hybrid theme or a plugin that brings the Customizer back. If a guide sends you to Appearance > Customize and that menu isn’t there, nothing is broken. Your theme puts those controls in the Site Editor.

Page builders such as Elementor and Divi add a third layer. When a page builder owns the header or a page, change it in the builder. If you change it in the theme instead, the builder can override your change.

Put each change in the layer that survives updates

Where you make a change matters more than which theme you have. WordPress’s Theme Handbook says a child theme lets you modify a theme without editing that theme’s own code. That matters because an update replaces the parent theme’s files, along with any edits you made to them.

The change	Where it belongs	What to watch
Brand colours, fonts, site-wide spacing	Styles in the Site Editor, or the theme’s Customizer options	One global colour can change links, buttons and notices across the site
One spacing fix, a hover state, a narrow override	Additional CSS (on block themes, CSS lives under Styles)	It is tied to the active theme and stays behind if you switch
Template markup, PHP, new functions	A child theme	Parent updates can still rename classes your code depends on
A redesign the theme fights at every step	A different base theme	Content carries over. Layout and theme-specific settings don’t

There are two catches. First, creating a child theme after you have customised a parent does not automatically copy those customisations across. Settings stored against the parent theme may have to be recreated in the child. Second, the advice in that WordPress.org thread differs for small and large changes. For small changes, find the element with your browser’s inspector and save an override in Additional CSS. For large changes, choose a theme that is already close to what you want. A bare starter theme has almost no styling, so you would be rebuilding the layout from scratch.

For a full walkthrough of each layer, see theme customization that survives updates.

Why a saved change often doesn’t show up

The most common complaint about theme customisation is a change that does nothing. There’s no error message. The page just looks the same. Check these causes in order, starting with the cheapest.

1. It was previewed, not published

WordPress.org’s Customizer documentation explains that you can try changes without publishing them. Nothing goes live until you click Publish. The Site Editor has its own Save button. When you live-preview a theme you haven’t activated yet, nothing is kept until you activate and publish it.

2. A cache is serving the old page

A site can have caches in several layers: the browser, a caching plugin or the theme’s own optimisation, the host’s server cache, and a CDN. Clearing one layer proves nothing about the others. Open the page in a private window, purge each layer, and regenerate any combined or minified CSS your optimisation plugin creates. Purging won’t fix a change that was never saved, though.

3. The CSS isn’t loading, or something else beats it

Right-click the element and choose Inspect. If your rule appears with a line through it, a more specific rule is winning. If it doesn’t appear at all, check the Network tab to see whether your stylesheet loads. In a child theme, the child stylesheet has to load after the parent’s, or the parent’s rules win. Our article on why a font change is not showing walks through this inspection step by step.

If the site breaks after a change instead of staying the same, you probably have a conflict, not a styling problem. Learn WordPress’s lesson on plugin and theme conflicts recommends this method: back up, work on a staging copy, deactivate plugins and reactivate them one at a time, and use error logs to find the cause. Our guide to plugins that stop working covers the same isolation process.

What to check before you choose a theme

A demo shows you what the theme can look like. It doesn’t show you what editing it will feel like six months after launch. Test these things instead.

• The editing model. A block theme gives you visual control over templates. A classic theme gives you whatever its panels expose. In WordPress’s 2023 annual survey, 45% of respondents said the Site Editor met their needs, so try it before committing.
• The changes you’ll make most. Open the theme’s documentation and check that the header, footer, mobile menu, content width and archive layout can be edited without code.
• Your plugins. If you run WooCommerce, a form plugin or a builder, build a real product page or form on a staging copy. A polished demo doesn’t prove compatibility.
• Maintenance. Look at the update history and the support channel. A plainer theme with clear templates is often cheaper to own than one packed with features.
• Lock-in. If your layout lives in a page builder, it goes with the builder. Builders are fast to work in. The cost shows up when you want to leave.

Your site will also never look exactly like the demo, because the demo uses its own images and copy. Import starter content onto a fresh install or a staging copy, not a live site. Installation problems are covered in installing a theme without breaking it.

Design changes can break what you can’t see

A change can look right and still make the site harder to use. W3C’s WCAG quick reference sets a minimum contrast ratio of 4.5:1 for normal-sized text. A darker brand colour on a button, or light grey body text, can fall below it. A common CSS reset removes focus outlines, and then keyboard users can’t see where they are on the page. After any colour or navigation change, check contrast, tab through the menu and forms, and make sure links still stand out by more than colour alone.

WooCommerce stores have one more risk. If your theme overrides WooCommerce templates, WooCommerce’s developer docs explain that WooCommerce sometimes updates its default templates in new releases, and your theme’s copies don’t update with them. WooCommerce’s System Status report, at WooCommerce > Status, lists outdated overrides. To fix one, back up the override, copy in the current template, reapply your changes and test. If you replace the file without reapplying your changes, you lose your customisation.

When the theme’s options run out

Sooner or later you will want a change that no setting covers. Your options, from simplest to biggest:

1. Find the element with the browser inspector and add a narrowly targeted rule in Additional CSS.
2. Put template or PHP changes in a child theme, so the parent can keep updating.
3. If almost every change is a fight, move to a theme that is closer to what you want, and test the move on staging first.
4. Hire someone, with a written scope and agreed milestones. Editing a template is a much smaller job than building custom functionality, so describe exactly which one you need.

If you would rather describe the change than track down the selector, SiteSelf takes requests like this in chat and makes them on your existing theme. Our page on having design changes made for you covers what that includes.

Whichever route you take, keep a short note of what changed and where: a setting, a CSS rule or a child-theme file. After the next theme or plugin update, that note tells you exactly what to check. Our guide to updating a theme without losing work covers that check.