Ruby file-attachment library created by Janko Marohnić after he forked from Refile. Design goals: work for any Ruby application (built on Rack, not Rails), no coupling to a specific ORM (thin integration with the persistence layer), modular plug-in architecture, multiple levels of abstraction so users can drop down to lower-level APIs, no DSLs (plain Ruby configuration), fully configurable to tune performance. Provides metadata validation plug-ins (file size, MIME type from content via chosen analyzer, image dimensions, custom metadata), processing on upload or on-the-fly (with URLs containing a custom alias + arguments rather than serialized processing steps), temporary + permanent storages to avoid orphan files, an upload-endpoint Rack app for direct uploads, and integration with Uppy and the tus protocol.