Open protocol (tus.io) for resumable file uploads, created by the same team as Uppy. Despite sounding intimidating, it is just a collection of HTTP headers and a URL convention that client and server agree on to achieve resumable uploads. Generic: many client and server implementations exist across languages. Usage flow: uploads go through a tus server, which translates them to the specific storage service API — the tus client doesn't know where files ultimately live. Uppy provides a tus plug-in, and a Ruby gem implements a tus server compatible with Uppy endpoints.