Title: is_subdomain_install
Published: April 25, 2014
Last modified: May 20, 2026

---

# is_subdomain_install(): bool

## In this article

 * [Return](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#return)
 * [Source](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#source)
 * [Related](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#related)
 * [Changelog](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#wp--skip-link--target)

Whether a subdomain configuration is enabled.

## 󠀁[Return](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#return)󠁿

 bool True if subdomain configuration is enabled, false otherwise.

## 󠀁[Source](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#source)󠁿

    ```php
    function is_subdomain_install() {
    	if ( defined( 'SUBDOMAIN_INSTALL' ) ) {
    		return SUBDOMAIN_INSTALL;
    	}

    	return ( defined( 'VHOST' ) && 'yes' === VHOST );
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/ms-load.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/7.0/src/wp-includes/ms-load.php#L18)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/7.0/src/wp-includes/ms-load.php#L18-L24)

## 󠀁[Related](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#related)󠁿

| Used by | Description | 
| [wp_initialize_site()](https://developer.wordpress.org/reference/functions/wp_initialize_site/)`wp-includes/ms-site.php` |

Runs the initialization routine for a given site.

  | 
| [get_oembed_response_data_for_url()](https://developer.wordpress.org/reference/functions/get_oembed_response_data_for_url/)`wp-includes/embed.php` |

Retrieves the oEmbed response data for a given URL.

  | 
| [show_blog_form()](https://developer.wordpress.org/reference/functions/show_blog_form/)`wp-signup.php` |

Generates and displays the Sign-up and Create Site forms.

  | 
| [network_step2()](https://developer.wordpress.org/reference/functions/network_step2/)`wp-admin/includes/network.php` |

Prints step 2 for Network installation process.

  | 
| [avoid_blog_page_permalink_collision()](https://developer.wordpress.org/reference/functions/avoid_blog_page_permalink_collision/)`wp-admin/includes/ms.php` |

Avoids a collision between a site slug and a permalink slug.

  | 
| [WP_MS_Sites_List_Table::prepare_items()](https://developer.wordpress.org/reference/classes/wp_ms_sites_list_table/prepare_items/)`wp-admin/includes/class-wp-ms-sites-list-table.php` |

Prepares the list of sites for display.

  | 
| [WP_MS_Sites_List_Table::get_sortable_columns()](https://developer.wordpress.org/reference/classes/wp_ms_sites_list_table/get_sortable_columns/)`wp-admin/includes/class-wp-ms-sites-list-table.php` |

Gets an array of sortable columns.

  | 
| [install_blog()](https://developer.wordpress.org/reference/functions/install_blog/)`wp-includes/ms-deprecated.php` |

Install an empty blog.

  | 
| [wpmu_validate_blog_signup()](https://developer.wordpress.org/reference/functions/wpmu_validate_blog_signup/)`wp-includes/ms-functions.php` |

Processes new site registrations.

  | 
| [wpmu_signup_blog_notification()](https://developer.wordpress.org/reference/functions/wpmu_signup_blog_notification/)`wp-includes/ms-functions.php` |

Sends a confirmation request email to a user when they sign up for a new site. The new site will not become active until the confirmation link is clicked.

  | 
| [get_blogaddress_by_domain()](https://developer.wordpress.org/reference/functions/get_blogaddress_by_domain/)`wp-includes/ms-deprecated.php` |

Get a full site URL, given a domain and a path.

  | 
| [get_blogaddress_by_name()](https://developer.wordpress.org/reference/functions/get_blogaddress_by_name/)`wp-includes/ms-blogs.php` |

Gets a full site URL, given a site name.

  | 
| [get_id_from_blogname()](https://developer.wordpress.org/reference/functions/get_id_from_blogname/)`wp-includes/ms-blogs.php` |

Retrieves a site’s ID given its (subdomain or directory) slug.

  | 
| [get_blog_details()](https://developer.wordpress.org/reference/functions/get_blog_details/)`wp-includes/ms-blogs.php` |

Retrieves the details for a blog from the blogs table and blog options.

  | 
| [ms_cookie_constants()](https://developer.wordpress.org/reference/functions/ms_cookie_constants/)`wp-includes/ms-default-constants.php` |

Defines Multisite cookie constants.

  |

[Show 10 more](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#)
[Show less](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#)

## 󠀁[Changelog](https://developer.wordpress.org/reference/functions/is_subdomain_install/?output_format=md#changelog)󠁿

| Version | Description | 
| [3.0.0](https://developer.wordpress.org/reference/since/3.0.0/) | Introduced. |

## User Contributed Notes

You must [log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fdeveloper.wordpress.org%2Freference%2Ffunctions%2Fis_subdomain_install%2F)
before being able to contribute a note or feedback.