Software as a Medical Device (SaMD) is defined by the International Medical Device Regulators Forum (IMDRF) as software intended to be used for one or more medical purposes that performs these purposes without being part of a hardware medical device. Unlike "Software in a Medical Device" (SiMD), which drives hardware (like the firmware in a pacemaker), SaMD is a standalone asset that can run on general-purpose platforms such as smartphones, tablets, or cloud servers.

The regulatory classification of SaMD depends on two factors: the state of the healthcare situation (Critical, Serious, or Non-Serious) and the importance of the information provided by the software to the healthcare decision. For an analysis of the various software categories—from diagnostic algorithms to digital therapeutics—the Software as a Medical Device Market overview provides a technical breakdown. This classification determines the level of clinical evidence required, ranging from simple verification/validation to prospective clinical trials.

A core characteristic of SaMD is its ability to be updated and iterated upon rapidly. This "Agile" development cycle poses a challenge for traditional regulatory frameworks designed for static hardware. Consequently, regulators are moving toward a "Total Product Life Cycle" (TPLC) approach, where the manufacturer’s quality management system (QMS) and post-market performance monitoring are as important as the initial pre-market clearance.