The reversal of current around an edge crack in a conductor induces an electromagnetic force that tends to open the crack in Mode I, potentially leading to fracture. In this study, we examine the influence of a uniform external magnetic field, applied perpendicular to the sample, on the fracture behavior of a metallic foil carrying an electric current. Experimental investigations were conducted by subjecting an 11 μm thick pre-notched aluminum foil to a series of electric current pulses in the presence of a low external magnetic field up to 0.4 T. Irrespective of the magnetic field, a sharp crack propagated from the notch tip once the nominal applied current density exceeded a critical value. However, the critical current density decreased linearly with the external magnetic field. Conjugate finite element analysis, employed to explore the interaction between the self-induced and the external magnetic fields, revealed a linear superposition of both magnetic fields. This coupling amplified the net crack opening stress, consistent with the observed experimental behavior. Furthermore, the transient stress intensity factor, KIE,t, evaluated for the critical combination of applied current density and external magnetic field demonstrated a reasonable match with the plane stress critical stress intensity factor, KIC, confirming the classic fracture condition of critical KIE,t ≥ KIC for crack propagation. This is the first study systematically highlighting the mechanisms governing crack propagation in thin conductors subjected to electric current and external magnetic fields simultaneously.