is_customize_preview

The timeline below displays how wordpress function is_customize_preview has changed across different WordPress versions. If a version is not listed, refer to the next available version below.

WordPress Version: 4.2

/**
 * Whether the site is being previewed in the Customizer.
 *
 * @since 4.0.0
 *
 * @global WP_Customize_Manager $wp_customize Customizer instance.
 *
 * @return bool True if the site is being previewed in the Customizer, false otherwise.
 */
function is_customize_preview()
{
    global $wp_customize;
    return $wp_customize instanceof WP_Customize_Manager && $wp_customize->is_preview();
}

WordPress Version: 4.0

/**
 * Whether the site is being previewed in the Customizer.
 *
 * @since 4.0.0
 *
 * @global WP_Customize_Manager $wp_customize Customizer instance.
 *
 * @return bool True if the site is being previewed in the Customizer, false otherwise.
 */
function is_customize_preview()
{
    global $wp_customize;
    return is_a($wp_customize, 'WP_Customize_Manager') && $wp_customize->is_preview();
}