One of the very first content-addressed storage servers, Venti, was originally developed for Plan 9 from Bell Labs and is now also available for Unix-like systems as part of Plan 9 from User Space. A first step towards an open source CAS+ implementation is Twisted Storage. Tahoe Least-Authority File Store is an open source implementation of CAS. Git is a userspace CAS filesystem. Git is primarily used as a source code control system.  git-annex is a distributed file synchronization system which uses content-addressable storage for files it manages. It relies on Git and symbolic links to index their filesystem location. Project Honeycomb is an open source API for CAS systems. The XAM interface being developed under the auspices of the Storage Networking Industry Association is an attempt to create a standard interface for archiving on CAS (and CAS like) products and projects. Perkeep is a recent project to bring the advantages of content-addressable storage "to the masses". It is intended to be used for a wide variety of use cases, including distributed backup; a snapshotted-by-default, version-controlled filesystem; and decentralised, permission-controlled filesharing. Irmin is an OCaml "library for persistent stores with built-in snapshot, branching and reverting mechanisms"; the same design principles as Git. Cassette is an open source CAS implementation for C#/.NET. Arvados Keep is an open source content-addressable distributed storage system. It is designed for large-scale, computationally intensive data science work such as storing and processing genomic data. Infinit is a content-addressable and decentralized (peer-to-peer) storage platform that was acquired by Docker Inc.  InterPlanetary File System (IPFS), is a content-addressable, peer-to-peer hypermedia distribution protocol.  casync is a Linux software utility by Lennart Poettering to distribute frequently-updated file system images over the Internet.