Danbooru
A taggable image board written in Rails
...Built using Ruby on Rails, it provides a robust tagging system that allows users to categorize images with highly structured metadata, enabling precise and flexible search queries. The platform supports advanced moderation workflows, including user roles, content approval systems, and reporting tools, making it suitable for large-scale community-driven repositories. It also includes features such as image uploads, comment threads, favorites, pools, and wiki pages that provide contextual information about tags and artists. Danbooru is optimized for performance and scalability, capable of handling millions of images while maintaining fast search and retrieval speeds.