- The correct title of this article is <<<ROOT>>>. The omission of the angle brackets is due to technical restrictions.
<<<ROOT>>> is the descriptor name used by the default constructor for Roblox's internal ClassDescriptor class. It is the name of the root static ClassDescriptor object. Since version 647 (October 2024), it is inherited by Object. Prior to that, it was inherited by Instance through DescribedBase. ClassDescriptor is internally used by the DescribedBase[1] class, which contains an internal pointer to a ClassDescriptor object.
The Instance:IsA method works by comparing the name of the class descriptor with the given string and, if that fails, calling the method on the base class descriptors recursively until there is no base and only then returning false. As a consequence, every instance class is considered to inherit from <<<ROOT>>> using the IsA method:
print(game:IsA("<<<ROOT>>>")) --> true
The <<<ROOT>>> class serves no purpose for game developers. It is exposed only through the IsA method and, until version 79 (December 2012), was shown in the API dump.[2]