One of the best parts about WordPress is how customizable it can be. Its open-source nature gives you a whole world of possibilities to explore. However, knowing how to do so correctly while maintaining your site’s integrity can be tricky – especially when it comes to the functions.php WordPress file.

Fortunately, it’s not as complicated as it sounds. By familiarizing yourself with the functions.php file, including when and how to use it, you can create a website tailored to your exact needs.

In this article, we’ll explore the purpose of the functions.php file and some things to know before you make any changes to it. We’ll also take you step-by-step through how to find it and add your alterations. Let’s get into it!

The Purpose of the functions.php File

The functions.php file comes with every WordPress theme. It’s a template that automatically loads once a theme has been downloaded and activated. For reference, here’s a sample of what the unaltered WordPress Twenty Twenty theme’s functions.php file looks like:

An image of the of the Twenty Twenty theme's functions.php WordPress file.

The code, written in the Hypertext Preprocessor (PHP) programming language, is critical to the functioning of your theme. The functions.php file can add or change features on your site depending on what the theme’s developer has included.

You can also access your theme’s functions.php file and modify it yourself to customize your WordPress site. You’re free to add, delete, or change any code you want.

The Difference Between the Core Functions File and the Theme Functions File

Themes aren’t the only place you’ll find a functions.php file. There’s also one in your site’s root directory. This is your core functions file.

While your core functions file may seem similar to the ones you find in themes, it’s imperative that you do not edit it. It contains information that’s vital to the running of your WordPress site. A mistake in this file could break your whole site.

Fortunately, this scenario is fairly easy to avoid. Whenever you’re about to edit a functions.php file, double-check that it’s located within a theme. This will lower the chances of making changes to the wrong part of your site.

Why You Might Need to Edit functions.php

When used correctly, functions.php can be an effective way to customize the look and feel of your site. For example, you can use it to create custom navigation menus, add new editor styles, and provide unique error messages.

You can also make more practical adjustments with the functions.php file. If you’re looking to add Google Analytics to your site, you can do so here. Editing it can also help you increase your site’s maximum upload size.

There are some changes you just can’t make through the WordPress Customizer alone. Whether you’re looking to implement a new aesthetic or make practical changes to your theme, a little familiarity with the functions.php file can go a long way.

Where to Find functions.php in WordPress (2 Key Locations)

If you’re interested in accessing your theme’s functions.php file, you can easily find it in two locations. Which one you should seek out depends on whether you’re editing an active or inactive theme, the scale of the changes you plan to make, and your personal preferences.

1. The themes Directory

The first place you can find your theme’s functions.php file is in your site’s themes directory. If you’re trying to access the file for an inactive theme, you’ll need to use this method. However, it can also be used for active themes.

This method requires the use of a File Transfer Protocol (FTP) client such as FileZilla. Open your FTP client of choice and navigate to your root directory (usually public_html):

Accessing the root directory in FileZilla to find the functions.php WordPress file.

Continue on to wp-content/themes/ and locate the folder for the theme you’d like to edit. In this example, we’ll go to wp-content/themes/twentytwenty/:

Accessing the Twenty Twenty WordPress theme files to find functions.php in FileZilla.

Once you’ve accessed the folder for the theme you want to change, you’ll find the functions.php file within it. Right-click on it to open it with your editor of choice and start making alterations.

This method is recommended if you’re planning to make extensive changes to your site’s theme. By editing functions.php using a third-party platform, you can work on it gradually and reupload it via FTP when you’re ready to apply your customizations.

2. The WordPress Theme Editor

If you’re making quick changes to an active theme and don’t want to use an FTP client, you can use the built-in WordPress theme editor to access functions.php. Start at your WordPress dashboard and navigate to Appearance > Theme Editor.

From the right-hand menu, select Theme Functions. This will bring up your theme’s functions.php file in a screen that looks similar to this:

The WordPress Theme Editor for the Twenty Twenty theme with functions.php selected.

From here, you can make alterations to the file as necessary. Just remember to click on Update File to save your changes when you’re done.

Key Considerations to Keep In Mind When Editing functions.php

Whenever you need to edit your theme’s functions.php file, you should consider using a child theme. A child theme operates identically to its parent theme while letting you customize it in a controlled environment. This protects the original theme from any mistakes you might make.

Additionally, customizing a child theme prevents theme updates from overriding your changes. Developer updates will apply to the parent theme and be inherited by the child theme, but your child theme’s files won’t be affected.

You can create a child theme manually by adding the required folders and files to your site’s themes directory, or use a plugin such as Child Theme Configurator:

The Child Theme Configurator plugin.

Even when using a child theme, there are some disadvantages to directly editing a functions.php file. One example is that any changes you make will only apply to the theme that the edited file belongs to. If you need to switch themes for some reason, your customizations won’t be carried over.

Furthermore, the functions.php file can become disorganized if you’re making several changes. Edits over time can become jumbled and messy. This can make undoing any of your additions a challenge.

Fortunately, the Code Snippets plugin provides an alternative to editing functions.php directly:

The Code Snippets plugin, which you can use to edit functions.php.

Code Snippets can come in handy in a lot of situations. For example, you might not be comfortable editing code. This plugin can help you manage your changes without having to access the functions.php file yourself.

This plugin can also help you keep multiple edits organized. This can make it easier to go back and review any changes. It’s also a powerful tool if you’re looking to apply a change to multiple themes without having to access each individual functions.php file.


Given its proximity to the rest of your site’s code, knowing exactly how to get to your WordPress theme’s functions.php file and change it successfully can be tricky. Fortunately, armed with a little bit of knowledge, you’ll be using it like a pro in no time.

In this article, we covered two ways to find and change your functions.php file:

  1. Use an FTP client to access your themes directory.
  2. Access the native theme editor within WordPress.

Do you have any questions about using the functions.php file? Let us know in the comments section below!

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