s3ql: S3QL is a file system that stores all its data online using storage s3ql: services like Google Storage, Amazon S3, or OpenStack. S3QL s3ql: effectively provides a hard disk of dynamic, infinite capacity that s3ql: can be accessed from any computer with internet access running Linux, FreeBSD or OS-X. S3QL is a standard conforming, full featured UNIX file system that is conceptually indistinguishable from any local file system. Furthermore, S3QL has additional features like compression, encryption, data de-duplication, immutable trees and snapshotting which make it especially suitable for online backup and archival. S3QL is designed to favor simplicity and elegance over performance and feature-creep. Care has been taken to make the source code as readable and serviceable as possible. Solid error detection and error handling have been included from the very first line, and S3QL comes with extensive automated test cases for all its components.