is_single() │ WP 1.5.0

Checks whether a post page (of any post type) is displayed. Posts with attachment and page post types will not be checked. Conditional tag.

You can specify a particular post or multiple posts to check if we are on the page of the specified post(s).

Use is_singular( $post_type ), when you need to check a post page by its type: post, page, or attachment, but not by a specific ID, title, slug.

Uses: WP_Query::is_single()
1 time — 0.00003 sec (very fast) | 50000 times — 0.02 sec (speed of light)

No Hooks.

Return

true|false. Whether the query is for an existing single post.

Usage

if( is_single( $post ) ){
	// ...
}
$post(int/string/array)

The post ID, post title or post slug, in order to identify a specific post.

You can pass an array of any of those values to check several posts.

The post is checked in the following order: ID, post_title, post_name.

Also, for tree-like posts (like page), you can pass the path: books/my-book in this case the search will be performed by the get_page_by_path() function.

Default: ''

Examples

0

#1 Various usage examples 

is_single();
// When any single Post page is being displayed.

is_single( '17' );
is_single( 17 );
// When Post 17 (ID) is being displayed.

is_single( 'Irish Stew' );
// When the Post with post_title of "Irish Stew" is being displayed.

is_single( 'beef-stew' );
// When the Post with post_name (slug) of "beef-stew" is being displayed.

is_single( [ 17, 'beef-stew', 'Irish Stew' ] );
// Returns true when the single post being displayed is either post ID 17,
// or the post_name is "beef-stew", or the post_title is "Irish Stew".
// Note: the array ability was added in version 2.5.

is_single( 'music/flamenko' );
// Will work for a treelike post with the name 'flamenko', child to a post with the name 'music'.
0

#2 Enqueue a CSS stylesheet for any single Post page 

if( is_single() ){
	wp_enqueue_style( 'handle', 'path/to/cssfile.css' );
}
0

#3 A note about the Cyrillic and name (slug)

If your website does not change the Cyrillic to the Latin alphabet - plugin Сry to Lat (or similar) is not installed, when a post is created its name changes and Cyrillic transforms to special symbols (ex: contacts will be changed to %d0%ba%d0%be%d0%bd%d1%82%d0%b0%d0%ba%d1%82%d1%8b), so when checking you need to take this into account. I.e. if the name (post_name) is checked instead of the title, do so:

is_single('моя-страница'); // wrong

is_single( sanitize_title('моя-страница') ); // correct

Notes

Changelog

Since 1.5.0 Introduced.

is_single() code WP 6.7.1

wp-includes/query.php 
function is_single( $post = '' ) {
	global $wp_query;

	if ( ! isset( $wp_query ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' );
		return false;
	}

	return $wp_query->is_single( $post );
}

Conditional tags (page type and request)

Conditional tags (all)

Queries

Main Functions