If human experience is any guide, operating effectively in unstructured environments -- like homes and offices -- requires robots to sense the forces during physical interaction. Yet, the lack of a versatile, accessible, and easily customizable tactile sensor has led to fragmented, sensor-specific solutions in robotic manipulation -- and in many cases, to force-unaware, sensorless approaches. With eFlesh, we bridge this gap by introducing a magnetic tactile sensor that is low-cost, easy to fabricate, and highly customizable. Building an eFlesh sensor requires only four components: a hobbyist 3D printer, off-the-shelf magnets (<5),aCADmodelofthedesiredshape,andamagnetometercircuitboard.Thesensorisconstructedfromtiled,parameterizedmicrostructures,whichallowfortuningthesensor′sgeometryanditsmechanicalresponse.Weprovideanopen−sourcedesigntoolthatconvertsconvexOBJ/STLfilesinto3D−printableSTLsforfabrication.Thismodulardesignframeworkenablesuserstocreateapplication−specificsensors,andtoadjustsensitivitydependingonthetask.OursensorcharacterizationexperimentsdemonstratethecapabilitiesofeFlesh:contactlocalizationRMSEof0.5mm,andforcepredictionRMSEof0.27Nfornormalforceand0.12Nforshearforce.Wealsopresentalearnedslipdetectionmodelthatgeneralizestounseenobjectswith95