[en] The critical currents of long uniform superconducting tin microbridges ranging in width from 0.3 to 10 μm have been measured. In the the narrowest bridges the current density is nearly uniform and the magnitude and temperature dependence of the critical-current density agree with the Ginzburg-Landau prediction. In wider bridges the current density becomes peaked at the edges of the film and the magnitude and temperature dependence of the critical current are altered. Theoretical calculations of the nonlocal linear electrodynamics together with adjustment of the nonlinear peak current density to include coherence-length effects appears adequate to explain both the magnitude and the temperature dependence of the critical currents in the wider bridges