High-field superconductors are characterized by a spin splitting of the density of states, giving rise to spin transport phenomena. This includes spin-polarized tunneling, spin-dependent thermoelectric effects, long-range quasiparticle spin transport, and spin-dependent coupling of supercurrents and quasiparticles. This review gives a brief overview of the theory background, recent experimental progress in the field, and an outlook on open problems and possible applications. High-field superconductors are characterized by a spin splitting of the density of states. Efficient spin injection and long-range coupled spin and heat transport are possible in the energy window of the spin splitting. In hybrid structures with ferromagnets, large thermoelectric effects appear. Experimental progress, open questions and application perspectives are reviewed. image