Can a standard object be used as a detail record in a master-detail relationship?

In a master-detail relationship on the Salesforce platform, the detail record must be a custom object. Standard objects cannot serve as detail records. This restriction exists because master-detail relationships are designed to maintain specific behaviors such as ownership, sharing rules, and cascade delete functionalities, which are not uniformly applicable when one of the records is a standard object.

In practical scenarios, this means that when setting up a master-detail relationship, one always needs to ensure that the detail record is a custom object, thus ensuring that all functionalities associated with this relationship are fully supported and work as intended. This approach maintains consistency across the database architecture and the relationships between objects within Salesforce.