Conditional Tags are a boolean data type that can be used in your Template Files to alter the display of content depending on the conditions that the current page matches. They tell WordPress what code to display under specific conditions. Conditional Tags usually work with PHP if /else Conditional Statements and have close relation with WOrdPress Template Hierarchy. .

Warning: You can only use conditional query tags after the WP_Query is set up or  with action hook.

Complete List of Conditional Tags

• is_front_page()
• is_home()
• is_front_page()
• is_home()
• is_admin()
• is_network_admin()
• is_admin_bar_showing()
• is_single()
• is_sticky()
• is_post_type_hierarchical( $post_type )
• is_post_type_archive()
• is_comments_popup()
• comments_open()
• pings_open()
• is_page()
• is_page_template()
• is_category( $category )
• is_tag()
• is_tax()
• has_term()
• term_exists( $term, $taxonomy, $parent )
• is_taxonomy_hierarchical( $taxonomy )
• taxonomy_exists( $taxonomy )
• is_author()
• is_date()
• is_year()
• is_month()
• is_day()
• is_time()
• is_new_day()
• is_archive()
• is_search()
• is_404()
• is_paged()
• is_attachment()
• wp_attachment_is_image( $post_id )
• is_local_attachment( $url )
• is_singular()
• post_type_exists( $post_type )
• is_main_query()
• is_new_day()
• is_feed()
• is_trackback()
• is_preview()
• in_the_loop()
• is_dynamic_sidebar()
• is_active_sidebar()
• is_active_widget( $widget_callback, $widget_id )
• is_blog_installed()
• is_rtl()
• is_multisite()
• is_main_site()
• is_super_admin()
• is_user_logged_in()
• email_exists( $email )
• username_exists( $username )
• is_plugin_active( $path )
• is_plugin_inactive( $path )
• is_plugin_active_for_network( $path )
• is_plugin_page()
• is_child_theme()
• current_theme_supports()
• has_post_thumbnail( $post_id )
• wp_script_is( $handle, $list )

The Conditions For …

All of the Conditional Tags test to see whether a certain condition is met, and then returns either TRUE or FALSE. The conditions under which various tags output TRUE is listed below. Those tags which can accept parameters are so noted.

The Main Page

• is_home()

The Front Page

• is_front_page()

The Blog Page

• is_front_page()
• is_home()

A Single Post Page

• is_single()

A PAGE Page

• is_page()
• is_page_template()

Has Post Thumbnail

• has_post_thumbnail( $post_id )

A Single Page, a Single Post, an Attachment or Any Other Custom Post Type

• is_singular()

A Category Page

• is_category( $category )

A Tag Page

• is_tag()
• has_tag()

A Taxonomy Page (and related)

• is_tax()
• has_term()
• term_exists( $term, $taxonomy, $parent )
• is_taxonomy_hierarchical( $taxonomy )
• taxonomy_exists( $taxonomy )

An Author Page

• is_author()

A Date Page

• is_date()
• is_year()
• is_month()
• is_day()
• is_time()
• is_new_day()

Any Archive Page

• is_archive()

A Search Result Page

• is_search()

A 404 Not Found Page

• is_404()

Is Dynamic SideBar

• is_dynamic_sidebar()

Is Sidebar Active

• is_active_sidebar()

Is Widget Active

• is_active_widget( $widget_callback, $widget_id )

Is User Logged in

• is_user_logged_in()

Email Exists

• email_exists( $email )

Username Exists

• username_exists( $username )

A Paged Page

• is_paged()

Right To Left Reading

• is_rtl()

An Attachment

• is_attachment()

Attachment Is Image

• wp_attachment_is_image( $post_id )

A Local Attachment

• is_local_attachment( $url )

Post Type Exists

• post_type_exists( $post_type )

Is Main Query

• is_main_query()

A New Day

• is_new_day()

A Syndication

• is_feed()

A Trackback

• is_trackback()

A Preview

• is_preview()

Has An Excerpt

• has_excerpt()

Has A Nav Menu Assigned

• has_nav_menu()

Is Blog Installed

• is_blog_installed()

Part of a Network (Multisite)

• is_multisite()
• is_main_site()
• is_super_admin()

An Active Plugin

• is_plugin_active( $path )
• is_plugin_inactive( $path )
• is_plugin_active_for_network( $path )
• is_plugin_page()

A Child Theme

• is_child_theme()

Theme supports a feature

• current_theme_supports()

Is Previewed in the Customizer

• is_customize_preview()