This paper seeks to further heritage theory and practice by considering decay as a transformative process contributing to heritage formation and value. Informed by our expertise in a variety of fields bordering heritage studies, we highlight the interplay of generative and degenerative aspects in different modes of decay and suggest that partnering with decay epistemologically, artistically, academically, practically, and democratically would allow heritage to be understood not as a rearguard action against loss but rather as a creative and generative process. To explore these ideas, we draw on several cases in geographical locations with unique socio-political and socio-environmental conditions, namely South Africa, Japan, Brazil, and Antarctica. We investigate different domains including archives and museums, heritage practices, landscapes, indigenous knowledge, environmental history, and nature conservation. We argue that decay is tightly linked to the concept of authenticity and acts as a code that holds a key to both past, present and future values of heritage, depending on the positionality and institutionalisation of the interpreter.