is_main_site( int $site_id = null, int $network_id = null )

Determine whether a site is the main site of the current network.

Parameters

$site_id

(int) (Optional) Site ID to test. Defaults to current site.

Default value: null

$network_id

(int) (Optional) Network ID of the network to check for. Defaults to current network.

Default value: null

Return

(bool) True if $site_id is the main site of the network, or if not running Multisite.

More Information

Replaces function is_main_blog(), deprecated since 3.0.0. (wp-includes/ms-deprecated.php)

Source

File: wp-includes/functions.php 

function is_main_site( $site_id = null, $network_id = null ) {
	if ( ! is_multisite() ) {
		return true;
	}

	if ( ! $site_id ) {
		$site_id = get_current_blog_id();
	}

	$site_id = (int) $site_id;

	return get_main_site_id( $network_id ) === $site_id;
}

Used By

Used By Description
wp-admin/includes/class-wp-ms-sites-list-table.php: WP_MS_Sites_List_Table::site_states()

Maybe output comma-separated site states.
wp-admin/includes/class-wp-site-health-auto-updates.php: WP_Site_Health_Auto_Updates::test_wp_version_check_attached()

Check if updates are intercepted by a filter.
wp-includes/option.php: delete_expired_transients()

Deletes all expired transients.
wp-admin/press-this.php: wp_load_press_this()
wp-includes/functions.php: _wp_upload_dir()

A non-filtered, non-cached version of wp_upload_dir() that doesn’t check the path.
wp-admin/includes/class-wp-ms-sites-list-table.php: WP_MS_Sites_List_Table::column_cb()

Handles the checkbox column output.
wp-admin/includes/upgrade.php: wp_should_upgrade_global_tables()

Determine if global tables should be upgraded.
wp-admin/includes/class-wp-automatic-updater.php: WP_Automatic_Updater::run()

Kicks off the background update process, looping through all pending updates.
wp-admin/includes/ms.php: avoid_blog_page_permalink_collision()

Avoids a collision between a site slug and a permalink slug.
wp-admin/includes/ms.php: wpmu_delete_blog()

Delete a site.
wp-admin/includes/upgrade.php: wp_upgrade()

Runs WordPress Upgrade functions.
wp-includes/class-wp-rewrite.php: WP_Rewrite::rewrite_rules()

Constructs rewrite matches and queries from permalink structure.
wp-includes/ms-functions.php: wp_schedule_update_network_counts()

Schedule update of the network-wide counts for the current network.
wp-includes/functions.php: get_dirsize()

Get the size of a directory.
wp-includes/ms-functions.php: maybe_redirect_404()

Correct 404 redirects when NOBLOGREDIRECT is defined.
wp-includes/ms-deprecated.php: is_main_blog()

Deprecated functionality to determin if the current site is the main site.

Changelog

Version Description
4.9.0 The $network_id parameter was added.
3.0.0 Introduced.

© 2003–2021 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/is_main_site