D’Arcy, R.T.P. JACoW Publishing Geneva, Switzerland In order to apply plasma wakefield accelerators for free electron lasers and/or colliders it is mandatory to reduce the beam energy spread from the many-percent-level down to 0.1% without affecting the beam emittance. Recently such reduction has been observed in particle-driven plasma-wakefield accelerators. The correlated energy spread is reduced by using the interaction of the electron bunch with its wakefields generated in the plasma. This contribution reviews the working principle of such a dechirper and the experimental observations in the different test facilities. A view on future directions and various ideas and concepts is presented.