The Medical Device Directive (MDD) defines the "essential requirements", as the requirements that every medical product has to fulfill, according to the scope they belong to. These essential requirements are described by Directive in Annex I.
The Medical Device Regulation (MDR) continues this approach with the "general safety and performance requirements", also in Annex I.
Examples of these requirements are the requirements for
The "general safety and performance requirements" in the MDR are described more in detail compared to the "essential requirements" in the MDD. Also new requirements have been introduced e.g. addressing medical devices containing nano particles, medicinal products (drugs) or tissue from human or animal origin.
The manufacturers themselves have to prove compliance with these essential requirements. To do so they have to follow one of the conformity assessment procedures described in the MDD respectively in the MDR.
Read here more about the conformity assessment procedures.
Typically manufacturers apply harmonized standards (or in future common specifications) to prove compliance with the essential respectively general safety and performance requirements. In particular, the MDR even insists on common specification "unless they can duly justify that they have adopted solutions that ensure a level of safety and performance that is at least equivalent thereto".