What is the Difference Between add_action and add_filter in WordPress?

One of the key reasons behind WordPress’s widespread adoption is its flexibility and ability to be customized to meet diverse needs.

At the core of this customization lies the concept of actions and filters.

In this blog, we will learn about WordPress hooks and understand how actions and filters allow developers to extend and enhance WordPress functionality.

What are WordPress Hooks?

In the context of WordPress, hooks are predetermined points in the code where developers can attach their custom code to modify the default behavior of the CMS. There are two main types of hooks: action hooks and filter hooks.

There are two types of Hooks in WordPress.

1. Action Hooks in WordPress

Actions are events that occur at specific moments during the execution of WordPress. With the add_action function, developers can register their custom functions to be executed when these events occur.

Actions are perfect for performing tasks without expecting any modified return value. For example, you might want to send a notification email when a new user is registered or update a custom field after a post is published.

2. WordPress Filter Hooks

Filters, on the other hand, allow developers to modify data before it is used or displayed. By using the add_filter function, custom functions can be attached to filters to alter data and return the modified value.

Filters are widely used to change the output of various WordPress functions, variables, and content. For instance, you can use a filter to modify the post excerpt length or change the logo URL in a theme’s header.

Difference Between add_action and add_filter in WordPress

While actions and filters are both powerful tools for customization, understanding their differences is crucial to using them effectively.

Actions are suitable when you want to perform specific tasks without altering data, while filters are designed to modify data and return the modified result.

For instance, if you want to display a custom message at the end of a post, an action is the way to go. On the other hand, if you want to add a prefix to post titles throughout your site, you should use a filter.

Let’s explain them with practical examples.

1. WordPress add_action Hook

This function is used to add new actions to the WordPress event system. An action is a specific point in the code where you can execute custom functionality.

When you use add_action, you are telling WordPress to execute a specific function (callback) at a particular action hook.

Actions are generally used to perform tasks without returning a modified value.

Here’s an example of using add_action:

function my_custom_function() {
  // Your custom code here

add_action('some_action_hook', 'my_custom_function');

In the example above, my_custom_function will be executed when the some_action_hook is triggered.

With add_action, you can extend the functionality of your themes and plugins without modifying their core code. This promotes maintainability and makes updates hassle-free.

2. WordPress add_filter Function

This function is used to add filters to WordPress. A filter allows you to modify a specific value by passing it through a callback function.

Unlike actions, filters typically accept a value, modify it, and return the modified value.

Filters are commonly used to change the output or behavior of functions, variables, or content.

Here’s an example of using add_filter:

function my_custom_filter($value) {
  // Modify $value here
  return $value;

add_filter('some_filter_hook', 'my_custom_filter');

In the example above, my_custom_filter will receive a value when the some_filter_hook is triggered. The function can modify the value and return the modified version.

How to Effectively Use Functions in WordPress?

To make the most of actions and filters, it’s essential to follow some best practices:

  • Always use unique hook names for your custom functions to prevent conflicts with other themes or plugins.
  • Avoid excessive use of hooks to maintain code readability and performance.
  • Use actions and filters only when necessary; sometimes, direct customization might be more appropriate.

Popular Use Cases of add_action and add-filter in WordPress

The WordPress ecosystem boasts an abundance of plugins and themes that utilize actions and filters to enhance functionality and user experience.

Popular plugins like WooCommerce, Yoast SEO, and Contact Form 7 leverage hooks to extend their capabilities. Many popular themes also rely heavily on actions and filters to offer flexible customization options.


Actions and filters are fundamental pillars of WordPress customization. By utilizing these hooks, developers can modify WordPress behavior and extend its capabilities in a structured and non-destructive manner.

Whether you are creating a custom theme, building a plugin, or simply making small tweaks to an existing site, understanding actions and filters helps you to harness the true power of WordPress and tailor it to your needs with elegance and precision.

So, go ahead and experiment with hooks – unlock the true potential of your WordPress website!