Fly Apps

A Fly App is an abstraction for a group of Machines running your code on Fly.io, along with the configuration, provisioned resources, and data we need to keep track of to run and route to your Machines.

Every Machine on Fly.io lives in a Fly App. Anycast IPs, certificates, Fly Volumes, and custom domains belong to apps as well.

Fly Launch commands, fly launch and fly deploy, create and update an app’s Machines as a unit with a single configuration and code base. Learn more about Fly Launch.

You can also create and configure Machines independently of other Machines in the same app, using fly machine run or the Machines API. See Run a new Machine for details about using fly machine run.

Fly Apps run on flyd. Learn more about how flyd works and how it came to be in the blog post: Carving the Scheduler Out of Our Orchestrator.