Aspects of the subject technology relate to ways to avoid file duplication in a cloud storage service. In some aspects, a method of the technology includes steps for retrieving, via a computer network, one or more files from a first memory location, identifying a first signature and a second signature for each of the files, and storing the first signature and the second signature into a duplication reference list. In some aspects, the method further includes steps for analyzing files in a second memory location to identify duplicate files using the duplication reference list. Systems and computer-readable media are also provided.