Add to ORKGThe technological prototype of the CALICE highly granular silicon-tungsten electromagnetic calorimeter (SiW-ECAL)was tested in a beam at DESY in 2017. The setup comprised seven layers of silicon sensors. Each layer comprised four sensors, with each sensor containing an array of 256 5:5 x 5:5 mm2 silicon PIN diodes. The four sensors covered a total area of 18 x 18 cm2, and comprised a total of 1024 channels. The readout was split into a trigger line and a charge signal line. Key performance results for signal over noise for the two output lines are presented, together with a study of the uniformity of the detector response. Measurements of the response to electrons for the tungsten loaded version of the detector are also presented