Fly Reference Guide

In Fly Reference, you'll find the definitive documentation for Fly features and Fly tools.

  • Architecture: A detailed view of Fly's implementation of Firecracker VMs, Scaling, Anycast networking, Proxies, and the Backhaul network, all of which come together to create Fly's infrastructure.

  • Builders: Fly supports multiple ways of assembling applications into deployable images. These are the builders and this section covers the four builders that currently exist on Fly.

  • Configuration and fly.toml: Each App on Fly.io has a configuration file called fly.toml which determines how the App is built, how its networking is configured, how the App scales and more. This section covers all the settings you can use.

  • Network Services: This section looks at Fly's networking and its support for IPv4 and IPv6 addresses via Anycast, automated TLS and HTTP middleware, proxies, and TCP passthrough.

  • Redis: The Redis key/value store is integrated into the Fly infrastructure and this section covers how you can access it to enable hashing and caching.

  • Regions: Fly's global locations are listed here so you can stay up to date with the expanding list.

  • Runtime Environment: This section covers the environment variables set when an App runs on Fly and the request headers which provide Apps with information about incoming connections.

  • Scaling: Fly is able to scale an App in various dimensions. This section looks at each and how to configure them for your App.

  • Secrets: Every App has a store for secrets. The secrets are exported to the running App through environment variables. Learn how to set and use secrets in this section and find out how they work with deployments to help secure your App.