wp-includes/class-wp-query.php:4683Determines whether the query is for an embedded post.
bool public function is_embed() { return (bool) $this->is_embed; }Introduced in 4.4.0. 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.