A proof of concept or PoC (from English proof of concept) is an implementation, often summarized or incomplete, of a method or idea, carried out with the purpose of verifying that the concept or theory in question can be exploited in a useful way.

PoC is commonly considered an important step in the process of creating a truly working prototype.

In computer security, proofs of concept are used to explain how zero-day vulnerabilities can be exploited. These are vulnerabilities whose exact functioning is unknown, and therefore PdC is used to try to understand how they can be exploited in a system or equipment.

The Oxford English Dictionary cites as the first use of the expression proof of concept in written language an article in the Los Angeles Times newspaper of January 22, 1967.

One of the first uses of the term was by Bruce Carsten in the context of a "Proof of Concept Prototype". Its meaning was defined in the magazine Power Conversion and Intelligent Motion, in its November 1989 issue, in the column titled Carsten's Corner (p. 38), which was subtitled with the legend "Let's define a few terms":.