If a WordPress theme update lost changes you’d paid for, the cause is almost always the same: someone edited the theme’s own files. An update replaces those files with the developer’s new version, so the edits go with them. The fix is to restore the old code, move it into a child theme, and update from there.
Key takeaways
- A theme update overwrites the theme’s files. Anything edited inside them is lost.
- Settings, Additional CSS and Site Editor changes live in the database, so they survive updates.
- A child theme holds your custom code separately, so the parent theme can update safely.
- Don’t stop updating the theme to protect your changes. Themes get security fixes too.
Why did my changes disappear after a theme update?
A theme is a folder of files on your server. When you update it, WordPress swaps that folder for the new version. It doesn’t merge your edits in, because it has no way of knowing they’re there.
WooCommerce’s guide puts it plainly: “all modifications are lost when theme files are overwritten during an update” (WooCommerce). WordPress’s own theme handbook warns that a function added to a theme’s functions.php will “disappear” the next time the theme updates (WordPress Developer Resources).
In our experience, the edit was usually a developer’s “quick change” made years earlier that nobody wrote down.
Which customisations survive an update, and which don’t?
Where a change was made decides whether it lasts. Here’s the short version:
| Where the change was made | Survives a theme update? |
|---|---|
| Edited theme files (style.css, functions.php, templates) | No |
| Appearance, then Theme File Editor in the dashboard | No, it edits the same files |
| Customizer settings and Additional CSS | Yes, stored in the database |
| Site Editor changes in a block theme | Yes, stored in the database |
| A child theme’s files | Yes |
| A code snippets plugin | Yes |
| Pages, posts and page-builder layouts | Yes, they’re content, not theme files |
The WooCommerce guide confirms that Additional CSS is stored “independently from the theme files”, and that a snippets plugin keeps PHP changes “safe from theme updates”. For block themes, WordPress says Site Editor changes are “stored in the database instead of the filesystem”.
What is a child theme, in plain English?
A child theme is a small theme that sits on top of your main (parent) theme. It borrows everything from the parent and only holds what you’ve changed. The parent can then update freely, and your changes stay put.
- It’s mostly empty. At minimum it has a style.css file whose “Template” line names the parent theme’s folder exactly.
- Its files win. A template file in the child theme replaces the parent’s version of that file.
- Both functions.php files run. The child’s loads first, then the parent’s, so you add code without copying the parent’s.
Can I get my lost customisations back?
Usually, yes, if you have a backup from before the update. Work through it in this order:
- Pause further updates. Turn off auto-updates for the theme so nothing else changes while you work.
- Find a backup from before the update. Restoring the theme folder alone is often enough. This is where website backups you can restore matter.
- Compare old and new files. A developer can compare the old theme files with the new ones line by line and pull out only your custom code.
- Move that code into a child theme. Custom functions, styles and template changes each go in their own file.
- Update the parent theme again, on a copy first. A WordPress staging site lets you test before customers see it.
One catch: WordPress saves Additional CSS against the active theme (WordPress code reference). When you switch to a new child theme, that box can look empty. Copy its contents somewhere safe before you switch, then paste them back.
Can’t I just stop updating the theme?
It’s tempting, but it swaps one problem for a bigger one. Patchstack counted 11,334 new WordPress vulnerabilities in 2025, and 9% of them were in themes (Patchstack). A frozen theme also drifts out of step with new WordPress, PHP and plugin versions.
Our guide on how often to update WordPress sets out a sensible rhythm for themes as well as plugins.
What does a properly built theme setup look like?
When we build or take over a WordPress site, we aim for a setup where updates are routine rather than risky:
- A child theme from day one, even if it starts nearly empty.
- Custom code in small, clearly named files inside the child theme, with comments saying what each one does and why.
- Nothing edited in the parent theme or in plugins. If a change can’t go in the child theme, it goes in a small custom plugin.
- WooCommerce template overrides checked after updates. WooCommerce lists outdated overrides under WooCommerce, then Status, then System Status (WooCommerce Developer Docs).
- Auto-updates switched on only once custom code is out of the parent. WordPress has offered theme auto-updates since version 5.5 (WordPress.org).
What should I ask my web developer?
- Is my site running a child theme? If not, have any theme files been edited?
- Where is the custom code kept, and is it documented?
- Have any WooCommerce or page-builder templates been overridden?
- Who tests theme updates, and on what copy of the site?
If nobody can answer, that’s the job our safe, tested WordPress updates service takes on. It’s included in all our website maintenance plans, with an off-site backup in place before anything changes.
If a different kind of update has broken your site, our guide to recovering from a WordPress update that broke your site covers plugins and WordPress itself.
Frequently asked questions
Do I need a child theme if I only use the Customizer?
Not strictly. Customizer settings and Additional CSS are stored in the database, so theme updates leave them alone. A child theme becomes essential as soon as anyone adds PHP code, edits a template or overrides WooCommerce files. Many developers set one up at the start anyway, so it’s ready when needed.
Can I add a child theme to a site that’s already live?
Yes. Create the child theme, move the custom code into it, copy across your Customizer settings and Additional CSS, then activate it. Do this on a staging copy first, because widgets, menus and settings can need reassigning when the active theme changes.
Do premium themes like Avada need a child theme?
Yes, if you add any custom code. Premium themes update just like free ones, and those updates replace the theme’s files the same way. Many premium theme sellers supply a ready-made child theme with the download, which is the easiest place to start.
How do I tell if my theme files have been edited?
Compare your theme folder with a fresh download of the same version from the theme’s seller or WordPress.org. Any differences are edits. A developer or maintenance provider can do this comparison quickly, and it’s worth doing before the next theme update arrives.
Sources
- Customizing WooCommerce: Best Practices, WooCommerce, accessed 13 November 2026
- Child Themes, WordPress Theme Handbook, accessed 13 November 2026
- wp_get_custom_css(), WordPress Code Reference, accessed 13 November 2026
- State of WordPress Security in 2026, Patchstack
- How to fix outdated WooCommerce templates, WooCommerce Developer Docs, accessed 13 November 2026
- Plugin and themes auto-updates, WordPress.org Documentation, updated 13 January 2023