wp-includes/class-wp-query.php:4328Determines whether the query is for an existing tag archive page.
$tagint|string|int[]|string[]optional''bool public function is_tag( $tag = '' ) { if ( ! $this->is_tag ) { return false; } if ( empty( $tag ) ) { return true; } $tag_obj = $this->get_queried_object(); if ( ! $tag_obj ) { return false; } $tag = array_map( 'strval', (array) $tag ); if ( in_array( (string) $tag_obj->term_id, $tag, true ) ) { return true; } elseif ( in_array( $tag_obj->name, $tag, true ) ) { return true; } elseif ( in_array( $tag_obj->slug, $tag, true ) ) { return true; } return false; }Introduced in 3.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-query.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.