Active Storage makes it simple to upload and reference files in cloud services
like Amazon S3, Google Cloud Storage, or Microsoft Azure Storage, and attach
those files to Active Records. Supports having one main service and mirrors in
other services for redundancy. It also provides a disk service for testing or
local deployments, but the focus is on cloud storage.

Files can be uploaded from the server to the cloud or directly from the client
to the cloud.

Image files can furthermore be transformed using on-demand variants for quality,
aspect ratio, size, or any other MiniMagick or Vips supported transformation.

See also: https://rubyonrails.org/