Electronic skins integrating both normal and shear force per taxel have a wide range of applications across diverse fields, including robotics, haptics and health monitoring. Current multi-axis tactile sensors often present complexities in structure and fabrication or require an extensive calibration process, limiting their widespread applications. Here we report an electronic soft magnetic skin capable of self-decoupling three-axis forces at each taxel. We use a simple sensor structure with customizable sensitivity and measurement range, reducing the calibration complexity from known quadratic (N2) or cubic (N3) scales down to a linear (3N) scale. The three-axis self-decoupling property of the sensor is achieved by overlaying two sinusoidally magnetized flexible magnetic films with orthogonal magnetization patterns. Leveraging the self-decoupling feature and its simple structure, we demonstrate that our sensor can facilitate a diverse range of applications, such as measuring the three-dimensional force distribution in artificial knee joints, teaching robots by touch demonstration and monitoring the interaction forces between knee braces and human skin during various activities.