AbstractSummaryWe describe a compression scheme for BUS files and an implementation of the algorithm in the BUStools software. Our compression algorithm yields smaller file sizes than gzip, at significantly faster compression and decompression speeds. We evaluated our algorithm on 533 BUS files from scRNA-seq experiments with a total size of 1TB. Our compression is 2.2× faster than the fastest gzip option 35% slower than the fastest zstd option and results in 1.5× smaller files than both methods. This amounts to an 8.3× reduction in the file size, resulting in a compressed size of 122GB for the dataset.Availability and implementationA complete description of the format is available athttps://github.com/BUStools/BUSZ-formatand an implementation athttps://github.com/BUStools/bustools. The code to reproduce the results of this article is available athttps://github.com/pmelsted/BUSZ_paper.