One of the greatest things about WordPress and WooCommerce is that you can modify and customize your website however you want, especially when you know how to add custom code to WooCommerce and WordPress. You can use numerous plugins, different themes, or extensions. You can even write your code to create a solution exactly for your needs. In this guide, you’ll learn the safest and most effective ways to add custom PHP code to your WooCommerce or WordPress site without breaking anything.
If you’re running a WordPress site or a WooCommerce store, sooner or later you’ll come across a situation where standard settings, themes, or plugins just don’t cut it. You may want to:
In most of these cases, there’s no plugin that does exactly what you need, or using a plugin would be overkill, adding unnecessary weight to your website. That’s when it’s time to add WooCommerce code snippets manually. Adding custom code in WooCommerce or WordPress allows you to tailor your site to your business needs without relying on third-party tools. You can control exactly what changes are made, keep your store lightweight, and avoid bloating your site with yet another plugin.
Custom code is ideal when:
Even simple changes, like redirecting users after adding a product to the cart, can require a few lines of code. Knowing how to safely add these changes is a must-have skill for any store owner who wants more control over their WooCommerce site.
In this article, we’ll show you how to add custom code to WooCommerce and WordPress the right way: afely, effectively, and without risking your site’s stability. Whether you’re a complete beginner or someone who has pasted code snippets before but wants to do it more cleanly, you’ll find step-by-step instructions and practical tips.
Learning how to safely add custom code to WooCommerce helps you gain more flexibility without increasing plugin overhead. Let’s get started with the best methods for adding custom code.
All three methods are working, but they differ in terms of complexity and safety. I will explain each of them in detail, but if you don’t know which solution to use, please read this paragraph first.
If you are a complete beginner in WordPress and the thought of adding custom code scares you, you can choose a plugin to add a custom code to WooCommerce and WordPress. This is the simplest solution, which doesn’t require any code knowledge skills. However, please have in mind, that those plugins may be the target of attacks on your website.
If you’re looking for the safest solution and you don’t want to be dependent on your theme, choose Must Use Plugins. Adding Must Use Plugins seems complicated, but if you learn this functionality, adding another custom code will be very easy. I can also add that this is the way recommended by our developers.
If creating Must Use Plugin is a little too much for you, you can use your child theme functions.php file. It’s also o good solution, but be careful and follow a few rules. Most of all, remember to add your code to a Child theme.
I don’t think I’ll surprise anyone with the fact that you can use a plugin to add custom code to WordPress. There are quite a few of them in the WordPress repository. In this article, I will show you how to use the Code Snippets plugin.
Easy solution…
This solution is getting more and more popular. Why is that? First of all, it is the simplest one. In most cases, all you have to do is just install an additional plugin, paste the code and everything is ready. It doesn’t require any knowledge of the code and paying additional attention. What’s more, all the plugins are free and available in the WordPress repository.
Its simplicity makes it an extremely tempting solution for beginner WordPress users. I get it. If you are a complete rookie, probably using a plugin to add your custom code is the right move. Unfortunately, this solution has its disadvantages.
…but not safe.
Have in mind that it’s not the safest solution. By their specific characteristics, plugins like Code Snippets may be the target of attacks on your website. If you want to use this option, remember to use regularly updated plugins, and additionally secure your website. However, it will be best if you’ll use one of the other solutions presented in that article.
Enough with all the descriptions and theories. It is time to move on to a proper guide.
To add a new snippet, just go to Snippets in the WordPress menu and click the Add New button. You can also use the Add New link in the WordPress menu directly.
On a new page, you can add your snippet. In this example, I’ll use the custom code from my earlier article on How to add a United Arab Emirates city in WooCommerce.
Enter the Title of your custom code. It should be self-describing so that you will be able to easily determine how it works. You can add a Description for additional information.
You can also add some tags, and priority. If everything is complete, save changes and activate the snippet.
You can do it on the same page or in the All Snippets list.
If the snippet is correct, your custom code should work well and be active on your website.
Another popular method to add WooCommerce custom code is by placing it directly into the functions.php file of your child theme. This is especially useful if you’re following tutorials that provide code snippets for WooCommerce customization. This is certainly the most popular solution for adding custom code in WordPress. In many articles or documentation, you can find information to add a certain code to the functions.php file of your theme. How to do it? It’s not that complicated.
We strongly recommend adding your custom code to the Child Theme functions.php file rather than to your original Theme. There are two main reasons to do that. If you add your custom code to the functions.php file of your regular theme, all the changes will be lost with each update of the theme. What’s more, it’s much more likely to crash your website by making a mistake in the code or deleting an important element of previously added code.
Remember that adding code to the functions.php file of your theme will make you dependent on it. If you decide to change your theme or debug an error on another theme, the code added earlier won’t work. That’s why this solution is best to add changes to your theme rather than adding changes to the website functionality.
Just go to Appearance > Theme Editor. Make sure that you are editing your Child Theme, and select Theme Functions (functions.php).
There you can paste your custom code.
Make sure there’s no closing ?> tag and Update File.
To do that, use File Manager of your cPanel or FTP client. In both situations go to public_html folder > [WordPress Folder] > wp-content > themes > [theme folder] > functions.php.
Open and edit that file. Scroll down the way to the end of the file, paste the code and save it. This method is better than using the WordPress Dashboard. If anything in the code is wrong and it’ll cause any issues on your website, it can easily be reverted.
Must Use Plugins, or simply mu-plugins, are plugins installed differently than regular plugins. They are installed in the wp-content/mu-plugins directory. Must Use Plugins don’t need (and cannot) be activated. They cannot be deactivated either. Plugins are active and work as long as they are in the mu-plugins directory.
Must Use Plugins are an ideal way to add additional functionality related to the site, things that should always work, even when you change your theme. It’s also a very secure solution. Adding Custom Code using Must Use Plugins is recommended by our developers.
As you will see, adding Must Use Plugin is not that difficult. First, in the wp-content directory create a new mu-plugins folder. You can use File Manager of your cPanel or FTP client. In the new directory, create a new file. I added just simply custom_code.php file. Open the file for editing and add your custom code. Remember to start with <?php, but don’t add closing ?> tag. Your code should look like this:
<?php
//your custom code
Save the file and Must Use Plugin should be active and working. Basically, you can use the mu-plugins like an old functions.php to add custom code to WooCommerce and WordPress. You can add many or even all of our snippets in one file.
You can find your Must Use Plugins in the WordPress Dashboard. Just go Plugins > Installed Plugins > Must-Use. It’ll be just the name of the file that you have added.
If you want to include additional information about the custom code in WordPress, you can add a typical plugin comment at the beginning of the file, with information about the name, author, and version:
/*
Plugin Name: My custom code
Description: Functions extending the capabilities of my website
Version: 1.0
Author: Bartosz Gajewski
*/
With that additional comment, your mu-plugin should look like this:
Yes, but only if done properly. Adding code through safe methods like the functions.php file of a child theme or using a code snippets plugin minimizes the risk of breaking your site. Always test your code on a staging site first and create a backup before making changes.
The safest and most beginner-friendly method is using a plugin like Code Snippets. It allows you to add, manage, and activate/deactivate custom code without directly editing theme files.
Yes, but only if you’re using a child theme. Editing the functions.php file of a parent theme is not recommended, as your changes will be overwritten after a theme update. A child theme ensures your code remains safe during updates.
It depends. Use a child theme if you’re comfortable editing code and need deeper customization. Use a plugin (like Code Snippets) if you want a safer, plugin-based interface to manage snippets. Both methods work, it’s about what suits your workflow best.
You can add various types of custom PHP code, such as:
Just make sure you understand what the code does and test before applying it to a live site.
That usually means there’s a syntax error in the code. If you can’t access your admin panel, use FTP or a file manager (e.g., in your hosting panel) to remove the faulty snippet or revert changes made in functions.php.
Yes, in many cases, custom code can replace lightweight plugins and help reduce bloat. However, for complex functionality, a well-built plugin may be more secure and better supported than writing it from scratch.
I hope this guide has helped you understand how to safely add custom code to WooCommerce and WordPress, whether you prefer using a plugin, editing the functions.php file, or creating Must Use Plugins. The methods described here are designed to make adding WooCommerce code snippets easier, safer, and more efficient. By choosing the right approach, you can customize your store without unnecessary plugins and maintain full control over your site’s functionality.
Content Writer at Octolize
Bartosz Gajewski is a content and marketing specialist with a solid background in SEO, WordPress content strategy, and technical documentation for digital products. With years of hands-on experience in both in-house and freelance roles, he supports tech companies – especially in the SaaS and e-commerce space – by creating content that informs, engages, and drives results.
His approach blends storytelling with data-driven SEO, and he’s been involved in projects ranging from rebranding and product marketing to growth experiments and copywriting for complex software tools. On the blog, he shares actionable insights from his work across marketing teams, product documentation, and online store optimization.
