BorgBackup is a deduplicating backup system that includes support for optional compression and encryption. A single Borg repository can store multiple archives, with the archives representing different folders, different points in time, different machines, or any combination thereof. Borg's deduplication is based on variable-length file chunking, with only chunks that aren't already present in a repository being added as new archives are created. An advantage of this approach is that it does not care at all about file names. As a consequence, files that occur in multiple archives will only be stored once and files can be moved or renamed without breaking the deduplication. This approach also means that only new portions of files are backed up. In addition to saving backups locally (e.g., to an external hard drive), Borg can also save them remotely on any machine that is reachable with an ssh connection. Borg's quick start guide gives a brief step-by-step example of how to use the software. The usage guide provides detailed information on all the software's features. In the installation section, users can find instructions on how to install Borg for their system as well as single-file executables of Borg that support Linux, macOS, and FreeBSD. Borg is free software, distributed under the 3-clause BSD license, with source code available on GitHub.