Swarm us a robust and fast clustering method for amplicon-based studies. The purpose of swarm is to provide a novel clustering algorithm to handle large sets of amplicons. Traditional clustering algorithms results are strongly input-order dependent, and rely on an arbitrary global clustering threshold. swarm results are resilient to input-order changes and rely on a small local linking threshold d, the maximum number of differences between two amplicons. swarm forms stable high-resolution clusters, with a high yield of biological information.