While hyperledger composer is a set of tools, APIs to model, build and deploy a business network on blockchain. Hyperledger fabric is blockchain framework implementation intended for developing solutions with a modular architecture. Composer runs on fabric. However, it lacks a lot of features of hyperledger fabric. It is a framework to accelerate the development of applications built on top of Hyperledger Fabric Composer allows you to model your roles, assets, and transactions and it can generate some of the lower-level code for you. With Hyperledger Fabric, you would be writing this code yourself.