In many contemporary democracies, political polarization increasingly involves deep-seated intolerance of opposing partisans. The decades-old contact hypothesis suggests that cross-partisan interactions might reduce intolerance if individuals interact with equal social status. We test this idea by implementing collaborative contact between over one thousand pairs of citizens with opposing political sympathies, using the online medium to credibly randomize participants’ relative social status within the interaction. Interacting as equals enhanced tolerant behaviors towards opposing partisans three weeks after contact, compared to interacting under conditions of inequality or to not interacting. These results demonstrate that a simple, scalable intervention that puts people on equal footing can reduce partisan intolerance and make online contact into a prosocial force.