Title: Functions | Page 37 of 49 | Developer.WordPress.org --- # Functions * function[is_email()](https://developer.wordpress.org/reference/functions/is_email/) * Verifies that an email is valid. * Used by [24 functions](https://developer.wordpress.org/reference/functions/is_email/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_email/#uses) | Source: [wp-includes/formatting.php:3551](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/formatting.php#L3551-L3634) * function[is_email_address_unsafe()](https://developer.wordpress.org/reference/functions/is_email_address_unsafe/) * Checks an email address against a list of banned domains. * Used by [1 function](https://developer.wordpress.org/reference/functions/is_email_address_unsafe/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_email_address_unsafe/#uses) | Source: [wp-includes/ms-functions.php:398](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/ms-functions.php#L398-L438) * function[is_embed()](https://developer.wordpress.org/reference/functions/is_embed/) * Is the query for an embedded post? * Used by [5 functions](https://developer.wordpress.org/reference/functions/is_embed/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_embed/#uses) | Source: [wp-includes/query.php:878](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L878-L887) * function[is_error()](https://developer.wordpress.org/reference/functions/is_error/) * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_error/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_error/#uses) | Source: [wp-includes/rss.php:706](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/rss.php#L706-L708) * function[is_favicon()](https://developer.wordpress.org/reference/functions/is_favicon/) * Is the query for the favicon.ico file? * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_favicon/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_favicon/#uses) | Source: [wp-includes/query.php:672](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L672-L681) * function[is_feed()](https://developer.wordpress.org/reference/functions/is_feed/) * Determines whether the query is for a feed. * Used by [7 functions](https://developer.wordpress.org/reference/functions/is_feed/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_feed/#uses) | Source: [wp-includes/query.php:413](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L413-L422) * function[is_front_page()](https://developer.wordpress.org/reference/functions/is_front_page/) * Determines whether the query is for the front page of the site. * Used by [7 functions](https://developer.wordpress.org/reference/functions/is_front_page/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_front_page/#uses) | Source: [wp-includes/query.php:466](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L466-L475) * function[is_gd_image()](https://developer.wordpress.org/reference/functions/is_gd_image/) * Determines whether the value is an acceptable type for GD image functions. * Used by [10 functions](https://developer.wordpress.org/reference/functions/is_gd_image/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_gd_image/#uses) | Source: [wp-includes/media.php:4120](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/media.php#L4120-L4128) * function[is_header_video_active()](https://developer.wordpress.org/reference/functions/is_header_video_active/) * Checks whether the custom header video is eligible to show on the current page. * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_header_video_active/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_header_video_active/#uses) | Source: [wp-includes/theme.php:1774](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/theme.php#L1774-L1797) * function[is_home()](https://developer.wordpress.org/reference/functions/is_home/) * Determines whether the query is for the blog homepage. * Used by [7 functions](https://developer.wordpress.org/reference/functions/is_home/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_home/#uses) | Source: [wp-includes/query.php:499](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L499-L508) * function[is_info()](https://developer.wordpress.org/reference/functions/is_info/) * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_info/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_info/#uses) | Source: [wp-includes/rss.php:694](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/rss.php#L694-L696) * function[is_lighttpd_before_150()](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/) * Determines whether the server is running an earlier than 1.5.0 version of lighttpd. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_lighttpd_before_150/#uses) | Source: [wp-includes/functions.php:6141](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/functions.php#L6141-L6146) * function[is_locale_switched()](https://developer.wordpress.org/reference/functions/is_locale_switched/) * Determines whether switch_to_locale() is in effect. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_locale_switched/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_locale_switched/#uses) | Source: [wp-includes/l10n.php:1916](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/l10n.php#L1916-L1921) * function[is_local_attachment()](https://developer.wordpress.org/reference/functions/is_local_attachment/) * Determines whether an attachment URI is local and really an attachment. * Used by [1 function](https://developer.wordpress.org/reference/functions/is_local_attachment/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_local_attachment/#uses) | Source: [wp-includes/post.php:6607](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/post.php#L6607-L6623) * function[is_login()](https://developer.wordpress.org/reference/functions/is_login/) * Determines whether the current request is for the login screen. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_login/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_login/#uses) | Source: [wp-includes/load.php:1336](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/load.php#L1336-L1338) * function[is_main_blog()](https://developer.wordpress.org/reference/functions/is_main_blog/) * Deprecated functionality to determine if the current site is the main site. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_main_blog/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_main_blog/#uses) | Source: [wp-includes/ms-deprecated.php:154](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/ms-deprecated.php#L154-L157) * function[is_main_network()](https://developer.wordpress.org/reference/functions/is_main_network/) * Determines whether a network is the main network of the Multisite installation. * Used by [4 functions](https://developer.wordpress.org/reference/functions/is_main_network/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_main_network/#uses) | Source: [wp-includes/functions.php:6454](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/functions.php#L6454-L6466) * function[is_main_query()](https://developer.wordpress.org/reference/functions/is_main_query/) * Determines whether the query is the main query. * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_main_query/#used-by) | Uses [4 functions](https://developer.wordpress.org/reference/functions/is_main_query/#uses) | Source: [wp-includes/query.php:902](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L902-L926) * function[is_main_site()](https://developer.wordpress.org/reference/functions/is_main_site/) * Determines whether a site is the main site of the current network. * Used by [18 functions](https://developer.wordpress.org/reference/functions/is_main_site/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_main_site/#uses) | Source: [wp-includes/functions.php:6410](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/functions.php#L6410-L6422) * function[is_month()](https://developer.wordpress.org/reference/functions/is_month/) * Determines whether the query is for an existing month archive. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_month/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_month/#uses) | Source: [wp-includes/query.php:553](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L553-L562) * function[is_multisite()](https://developer.wordpress.org/reference/functions/is_multisite/) * Determines whether Multisite is enabled. * Used by [173 functions](https://developer.wordpress.org/reference/functions/is_multisite/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_multisite/#uses) | Source: [wp-includes/load.php:1448](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/load.php#L1448-L1458) * function[is_multi_author()](https://developer.wordpress.org/reference/functions/is_multi_author/) * Determines whether this site has more than one author. * Used by [0 functions](https://developer.wordpress.org/reference/functions/is_multi_author/#used-by) | Uses [4 functions](https://developer.wordpress.org/reference/functions/is_multi_author/#uses) | Source: [wp-includes/author-template.php:607](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/author-template.php#L607-L625) * function[is_nav_menu()](https://developer.wordpress.org/reference/functions/is_nav_menu/) * Determines whether the given ID is a navigation menu. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_nav_menu/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_nav_menu/#uses) | Source: [wp-includes/nav-menu.php:62](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/nav-menu.php#L62-L79) * function[is_nav_menu_item()](https://developer.wordpress.org/reference/functions/is_nav_menu_item/) * Determines whether the given ID is a nav menu item. * Used by [3 functions](https://developer.wordpress.org/reference/functions/is_nav_menu_item/#used-by) | Uses [2 functions](https://developer.wordpress.org/reference/functions/is_nav_menu_item/#uses) | Source: [wp-includes/nav-menu.php:238](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/nav-menu.php#L238-L240) * function[is_network_admin()](https://developer.wordpress.org/reference/functions/is_network_admin/) * Determines whether the current request is for the network administrative interface. * Used by [16 functions](https://developer.wordpress.org/reference/functions/is_network_admin/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_network_admin/#uses) | Source: [wp-includes/load.php:1407](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/load.php#L1407-L1415) * function[is_network_only_plugin()](https://developer.wordpress.org/reference/functions/is_network_only_plugin/) * Checks for “Network: true” in the plugin header to see if this should be activated only as a network wide plugin. The plugin would also work when Multisite is not enabled. * Used by [6 functions](https://developer.wordpress.org/reference/functions/is_network_only_plugin/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_network_only_plugin/#uses) | Source: [wp-admin/includes/plugin.php:605](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-admin/includes/plugin.php#L605-L611) * function[is_new_day()](https://developer.wordpress.org/reference/functions/is_new_day/) * Determines whether the publish date of the current post in the loop is different from the publish date of the previous post in the loop. * Used by [1 function](https://developer.wordpress.org/reference/functions/is_new_day/#used-by) | Uses [0 functions](https://developer.wordpress.org/reference/functions/is_new_day/#uses) | Source: [wp-includes/functions.php:1018](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/functions.php#L1018-L1026) * function[is_object_in_taxonomy()](https://developer.wordpress.org/reference/functions/is_object_in_taxonomy/) * Determines if the given object type is associated with the given taxonomy. * Used by [12 functions](https://developer.wordpress.org/reference/functions/is_object_in_taxonomy/#used-by) | Uses [1 function](https://developer.wordpress.org/reference/functions/is_object_in_taxonomy/#uses) | Source: [wp-includes/taxonomy.php:4969](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/taxonomy.php#L4969-L4975) * function[is_object_in_term()](https://developer.wordpress.org/reference/functions/is_object_in_term/) * Determines if the given object is associated with any of the given terms. * Used by [2 functions](https://developer.wordpress.org/reference/functions/is_object_in_term/#used-by) | Uses [7 functions](https://developer.wordpress.org/reference/functions/is_object_in_term/#uses) | Source: [wp-includes/taxonomy.php:4898](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/taxonomy.php#L4898-L4958) * function[is_page()](https://developer.wordpress.org/reference/functions/is_page/) * Determines whether the query is for an existing single page. * Used by [5 functions](https://developer.wordpress.org/reference/functions/is_page/#used-by) | Uses [3 functions](https://developer.wordpress.org/reference/functions/is_page/#uses) | Source: [wp-includes/query.php:584](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/query.php#L584-L593) [Previous Page](https://developer.wordpress.org/reference/functions/page/36/?output_format=md) [1](https://developer.wordpress.org/reference/functions/?output_format=md) … [35](https://developer.wordpress.org/reference/functions/page/35/?output_format=md) [36](https://developer.wordpress.org/reference/functions/page/36/?output_format=md) 37 [38](https://developer.wordpress.org/reference/functions/page/38/?output_format=md) [39](https://developer.wordpress.org/reference/functions/page/39/?output_format=md)… [49](https://developer.wordpress.org/reference/functions/page/49/?output_format=md) [Next Page](https://developer.wordpress.org/reference/functions/page/38/?output_format=md)