How to Edit functions.php Without Breaking Your Site

The functions.php file powers custom theme behaviour, but one typo can crash your whole site. Here’s how to edit it without risk.

Always use a child theme

Edit functions.php in a child theme, never the parent — otherwise updates erase your code. The child’s functions file adds to the parent’s rather than replacing it, keeping your changes safe.

Back up and test on staging

Before editing, back up the file and ideally test changes on a staging site. A syntax error here causes a white screen, so having a quick way to revert is essential.

Know how to recover

If an edit breaks the site, restore the previous functions file via File Manager or FTP, or remove the offending snippet. Keep a copy of the working version before you start.