paperclip

The legacy gold standard for file attachment management in Ruby on Rails applications.

Developed by Thoughtbot, Paperclip simplified file uploads for over a decade by treating attachments like any other model attribute. It integrates directly with ImageMagick to handle transformations (resizing and cropping) and supports storage backends like Amazon S3 and Fog. While the library was officially deprecated in 2018 in favor of Active Storage, it remains a critical component in thousands of production environments (maintaining over 9,000 stars on GitHub) due to its robust validation system and straightforward migration paths.

https://github.com/thoughtbot/paperclip