Like Ruby on Rails, Merb is an MVC framework. Unlike Rails, Merb is ORM-agnostic, JavaScript library agnostic, and template language agnostic, preferring plugins that add in support for a particular feature rather than trying to produce a monolithic library with everything in the core. In fact, this is a guiding principle of the project, which has led to third-party support for the ActiveRecord, DataMapper, and Sequel ORMs.