casync (content-addressable synchronisation) is a Linux software utility designed to distribute frequently-updated file system images over the Internet.

[2][3] According to the creator Lennart Poettering, casync is inspired by rsync and Git,[4] as well as tar.

[5] casync is aimed to be used for Internet of things (IoT), container, virtual machine (VM), portable services, and operating system (OS) images, as well as backups and home directory synchronization.

[3] casync splits images into variable size segments, uses sha256 checksums, and aims to work with content delivery networks (CDNs).

[5] Similar software that delivers file system images are:[4]