Using WordPress ‘register_sidebar_defaults’ PHP filter

‘register_sidebar_defaults’ is a WordPress PHP filter that allows you to modify the default arguments of a sidebar before it’s registered.


To use this filter, add a custom function to your theme’s functions.php file or a plugin, and hook it to the register_sidebar_defaults filter.

function custom_register_sidebar_defaults( $defaults ) {
    // Modify the defaults array here
    return $defaults;
add_filter( 'register_sidebar_defaults', 'custom_register_sidebar_defaults' );


  • $defaults (array): The default sidebar arguments that can be modified.


Change the Default Sidebar Title

function change_default_sidebar_title( $defaults ) {
    $defaults['name'] = 'My Custom Sidebar';
    return $defaults;
add_filter( 'register_sidebar_defaults', 'change_default_sidebar_title' );

This code changes the default sidebar title to “My Custom Sidebar”.

Update Default Sidebar Description

function update_default_sidebar_description( $defaults ) {
    $defaults['description'] = 'This is a custom sidebar description.';
    return $defaults;
add_filter( 'register_sidebar_defaults', 'update_default_sidebar_description' );

This code updates the default sidebar description to “This is a custom sidebar description.”

Change Default Sidebar Before and After Widget Markup

function change_default_sidebar_widget_markup( $defaults ) {
    $defaults['before_widget'] = '<div class="custom-widget">';
    $defaults['after_widget'] = '</div>';
    return $defaults;
add_filter( 'register_sidebar_defaults', 'change_default_sidebar_widget_markup' );

This code changes the default markup for widgets within the sidebar, wrapping them in a <div> with the class custom-widget.

Modify Default Sidebar Before and After Title Markup

function modify_default_sidebar_title_markup( $defaults ) {
    $defaults['before_title'] = '<h3 class="custom-title">';
    $defaults['after_title'] = '</h3>';
    return $defaults;
add_filter( 'register_sidebar_defaults', 'modify_default_sidebar_title_markup' );

This code modifies the default markup for the sidebar titles, wrapping them in an <h3> tag with the class custom-title.

Customize Default Sidebar Class and ID

function customize_default_sidebar_class_and_id( $defaults ) {
    $defaults['class'] = 'my-custom-sidebar';
    $defaults['id'] = 'unique-sidebar-id';
    return $defaults;
add_filter( 'register_sidebar_defaults', 'customize_default_sidebar_class_and_id' );

This code customizes the default sidebar class to “my-custom-sidebar” and sets a unique ID “unique-sidebar-id” for the sidebar.