Any instrument, apparatus, appliance, software, implant, reagent, material, or another article can be a medical device. An app, therefore, can also be a medical device. The extensive definition of medical device is given in article 2 of the MDR.
The determination of whether something is a medical device is based on the intended (medical) purpose. The intended purpose describes what the product is designed to do. Therefore, it is recommended to first establish an intended purpose for the product. Consider how the product will be put on the market, for which user group and/or patient group it is intended and which claims will be made on the website and in advertising material.
An exception are in vitro diagnostic medical devices. These medical devices are not controlled by the MDR but by the In vitro diagnostic medical devices regulation (IVDR). The definition of an in vitro medical device is given in article 2 of the IVDR.
Note: The MDR and IVDR designate medical device accessories (e.g. attachments and accessories) and a special group of non-medical products (described in Annex XVI of the MDR) also as "medical devices". Therefore, they also have to meet the requirements of the MDR/IVDR and obtain CE certification before they can be placed on the market.