A coherent interface between temporal and spatial degrees of freedom (DOFs) allows one to use photons to take advantage of both types of DOF in quantum information processing. Previous interfaces either suffer from a typical loss of 1–3 dB or disturb the polarization DOF in the conversion process. Here we realize a low-loss polarization-independent coherent interface between temporal and spatial DOFs, specifically the time-bin and path modes. The experimental loss is 0.2 dB, and the fidelity of the conversion process is found by tomography to be 0.970 (0.947) without (with) considering the polarization DOF. As an application, our interface transforms a time-bin qubit output from an entanglement distribution channel to a path qubit, which allows postselection-loophole-free measurement of the Bell inequality. With its low loss and polarization independence, our interface promises applications in coherent conversion from hybrid temporal-polarization states to spatial-polarization states and could be put into a cavity to boost the generation rate of multiphoton polarization-entangled sources or enhance the scalability of sequential quantum metrology.