The Key4hep turnkey software stack for future colliders

High Energy Physics experiments for the future depend on reliable, proven, and flexible software components to perform detector optimisation and physics performance studies. Key4hep is a software stack designed to provide a set of software components for future and present High Energy Physics projects. In these proceedings the main components of Key4hep are described, comprising: EDM4hep for the common event data model, simulation interfaces for both Delphes and Geant4, k4MarlinWrapper to integrate with various iLCSoft components, and software tools to build, validate and integrate the different components of Key4hep seamlessly. It provides a software infrastructure for easy access and use of its components, where different future collider projects are adapting to use Key4hep, such as FCC, CEPC, ILC, CLIC and SCT. These adaptations showcase the feasibility of the software stack as a turnkey solution for nascent physics studies and as a base for future High Energy Physics experiments.