Editing Widget Parameters per Filter Function WordPress

If you want to change the parameters of the default widgets, for instance the font sizes of the tag cloud widget, you will notice that you can’t access the codes directly.

Editing the core files in the /wp-includes folder is obviously not an option.

Luckily, most of the default widgets are now applying filters to the parameters;
for example, in this the line the filter gets applied for the  tag cloud widget – in /wp-includes/default-widgets.php:

wp_tag_cloud( apply_filters('widget_tag_cloud_args', array('taxonomy' => $current_taxonomy) ) );

Add a filter function to functions.php of your theme;
for example changing the font size range for the tags:

(corrected 05 Feb 2013)

function set_tag_cloud_sizes($args) {
$args = array_merge( $args, array('smallest' => 12, 'largest' => 19) );
return $args; }

Alternative code:

function set_tag_cloud_sizes($args) {
$args['smallest'] = 12;
$args['largest'] = 19;
return $args; }

Another example – to show only tags from the current single post:

function single_post_tag_cloud_tags($args) {
if( is_single() && $args['taxonomy'] == 'post_tag' ) {
global $post;
$post_tag_ids = wp_get_post_tags( $post->ID, array( 'fields' => 'ids' ) );
$args = array_merge( $args, array('include' => implode(',',$post_tag_ids)) );
return $args;

See the codex chapter of wp_tag_cloud()   for all possible parameters.

Another similar example – excluding the default category ‘uncategorized’ from the category widget:

function exclude_default_cat($args) {
$args['exclude'] = '1';
return $args;

A further example – removing the output of the category description as title attributes in the category widget:

function remove_cat_description_widget($args) {
$args['use_desc_for_title'] = 0;
return $args;

Here is the list of all filters for the default widgets:


Adding a Custom Widget Area to a WordPress Template

The Codex has a chapter on how to add new widget areas (commonly referred to as ‘sidebars’) to a theme’s template: ‘Widgetizing Themes

This example here is to give you the direct code to add to functions.php and to the template of your theme.

First step: register the custom sidebar

– this goes into functions.php:

'name'         => 'Custom Widget Area',
'id'            => 'custom-widgets',
'description'   => 'a custom widget area',
'before_widget' => '<li id="%1$s">',
'after_widget'  => '</li>',
'before_title'  => '<h2>',
'after_title'   => '</h2>'    ));

Second step: the custom div with the dynamic ‘sidebar’

– this goes into the template at the location where you want the custom widget to appear:

<?php if ( is_active_sidebar( 'custom-widgets' ) ) : ?>
<div class="custom"><ul>
<?php if ( !dynamic_sidebar( 'custom-widgets' ) ) : ?>
<?php endif; ?>
<?php endif; ?>

The outer conditional statement makes sure that the custom div with the widget is only shown if there is actually an active widget in the custom area.

The most basic code to output the widget would be:

<?php dynamic_sidebar( 'custom-widgets' ); ?>

The parameter for registering the widget are taken from the example in the codex; you need to adapt them to fit the existing structure of your theme.
You will of course need to add some styles to format the new custom widget area according to your ideas;
for instance to style the title and to suppress the bullets:

.custom .widgettitle { font-family: arial, sans-serif; }
.custom ul { list-style-type: none; }