Fly.io

Fly.io runs your container as a Machine (a VM) in a region you choose. You scale by starting more Machines, and you pay for the ones that are running.

At a glance

What it is	A public-cloud VM host aimed at running containers close to users. The unit is a Machine.
Use it for	An API that must stay in a specific region, with a volume for data, when a few dollars a month is an acceptable floor.
Don't use it for	A free always-on service. New organizations have no free allowance.
Free tier (checked 2026-11-01)	No free tier for new organizations, and no monthly free usage allowance. Organizations still on plans discontinued in October 2024 keep their old allowances. Pricing update, effective 2026-10-01. Pricing.
Pricing model (checked 2026-11-01)	Cheapest always-on example: shared-cpu-1x, 256 MB, in Ashburn (iad) or Secaucus (ewr), $2.19 per 30 days ($0.0030/hour), plus egress. Egress is $0.02/GB in North America and Europe, $0.04/GB in Asia Pacific, Oceania, and South America, and $0.12/GB in Africa and India. Extra RAM is $6/GB/month, up to 128 GB. Volumes are $0.15/GB/month provisioned. Snapshots are $0.08/GB/month, with the first 10 GB free. A stopped Machine's rootfs is $0.15/GB/month. A dedicated IPv4 is $2/month. Shared IPv4 and IPv6 are free. The first 10 single-hostname certificates are free, then $0.10/month each. A wildcard certificate is $1/month. Support plans (Standard $29/month, Premium $199/month) are support, not the compute floor. About pricing.
CLI and latest version (checked 2026-11-01)	flyctl v0.5.1, published 2026-10-29 (a fly skills command and deploy operation spans). GitHub release.
Official docs	fly.io/docs

Core concepts

• App: a name, a config file, and a set of Machines.
• Machine: one VM running one image. It has a size, a region, and a state (started or stopped).
• Volume: persistent disk in one region. It does not follow a Machine to another region by itself.
• fly.toml: the app config. Image, services, checks, and VM size live here.
• Region: a three-letter code. The cheapest always-on example above is iad or ewr. List them with fly platform regions (verify the live list).
• Postgres: not a separate serverless product. It is a Machine plus a volume (the fly postgres tooling, or a container you run yourself).
• Secrets: fly secrets set injects environment variables. Setting one restarts the Machines.
• Anycast IP: shared IPv4 and IPv6 are included. A dedicated IPv4 costs $2/month.

Deploy

Dashboard

1. Create an app and pick the organization. New organizations do not get a free allowance (checked 2026-11-01).
2. You can launch from a GitHub repo in the dashboard. If that screen stalls, deploy with flyctl instead. A dashboard Git connection is optional.
3. Set secrets in the app's secret list. They are not in fly.toml.
4. Add a certificate for the custom domain. The first 10 single-hostname certificates are free. Point DNS at the app's addresses.
5. Roll back by deploying the previous image tag (Machines, Release history, or the CLI below).

CLI

1. fly auth login, then fly launch in the project. Answer the region and the size. Decline a Postgres cluster unless you want one.
2. fly secrets set DATABASE_URL=... (the value comes from your password manager, not from the shell history if you can avoid it).
3. fly deploy builds and rolls the Machines.
4. fly certs add app.example.com requests a certificate. example.com here is a placeholder.
5. Roll back: fly releases and fly deploy --image <registry>/<app>:<previous-tag> (verify the flag with fly deploy --help).

Config file

fly.toml. Reference: app configuration.

app = "my-api"
primary_region = "iad"

[build]
  dockerfile = "Dockerfile"

[http_service]
  internal_port = 8080
  force_https = true
  auto_stop_machines = "stop"
  auto_start_machines = true
  min_machines_running = 0

[[vm]]
  size = "shared-cpu-1x"
  memory = "256mb"

The auto_stop_machines value is the current style of "stop when idle". verify the allowed values in the configuration reference before you copy this, because the key has changed names before. Secrets are not in the file. A volume is created with fly volumes create and mounted from this file (verify the [mounts] block against the reference).

Common patterns

• Monorepo: set the build context and Dockerfile path in fly.toml so the image builds from the service directory.
• Preview per pull request: Fly does not create one automatically the way Vercel does. A review app is a separate Fly app, usually created from CI (verify if a first-party preview product exists now).
• Scheduled work: a second Machine, or a process that uses the Machines API on a schedule. There is no single "cron" product name confirmed here (verify).
• Postgres: run it as a Machine with a volume in the same region as the API. You pay for the volume even when you plan the size carefully. For a managed Postgres with auth, use Supabase and point the Machine at the pooler.
• Idle: you can stop a Machine when it has no traffic and start it on the next request. Stopped rootfs is still billed ($0.15/GB/month, checked 2026-11-01). Cold start is the trade.

Gotchas

• No free tier for new orgs (effective 2026-10-01). A "free hobby" note from 2024 does not apply to a new organization.
• Egress (checked 2026-11-01): the $2.19 machine is not the whole bill. Traffic out is priced by continent.
• Volumes are regional and billed provisioned, not on bytes used ($0.15/GB/month).
• Region pinning: the Machine runs where you started it. A volume cannot be mounted from another region. Moving region means creating a new volume and copying data.
• Stopped is not free: rootfs of a stopped Machine is $0.15/GB/month (checked 2026-11-01).
• IPv4: shared IPv4 is free. Dedicated is $2/month. Some DNS setups want a dedicated address (verify your registrar's requirements).
• Config keys: do not copy auto_stop_machines from an old blog post without checking the reference.

What's new in recent releases

• 2026-10-01: pricing update. No free allowance for new organizations. The machine, egress, volume, snapshot, and certificate prices above are from that schedule. Pricing update.
• 2026-10-29: flyctl v0.5.1. Release.
• Checked 2026-11-01 on fly.io/docs/about/pricing: stopped Machine rootfs $0.15/GB/month, volumes $0.15/GB/month, first 10 GB of snapshots free. A longer product changelog was not confirmed (verify community.fly.io or the docs changelog if you need a third feature note).

Connects to

• Render and Railway: container hosts that trade region control for a simpler free or trial plan.
• Docker: the image a Machine runs.
• CI/CD: fly deploy from GitHub Actions when you want the same pipeline shape as the VPS.
• Self-host a Docker stack: one server instead of per-Machine billing.
• Compute: EC2 and Fargate, the AWS versions of this choice.