Creating Fly App

When to use this page

• You are deploying a backend application on Fly.io.
• You need to initialize fly.toml and create the base app resource.

Prerequisites

• flyctl installed and authenticated.
• Dockerfile available for the app (or buildpack-ready project).
• Target Fly organization selected.

Fly Apps are the core deployment unit on Fly.io. Each app runs as a micro-VM (Machine) in your chosen region.

Documentation: https://fly.io/docs/launch/create/

Key features

• Deploy Docker containers or buildpack-based apps
• Multi-region deployment support
• Built-in load balancing and TLS termination
• Auto-scaling based on demand

Step 1: Create app

Create a new Fly app using the CLI:

fly apps create <app-name> --org <org-name>

• Make sure to select the correct organization
• Pick a primary region closest to your users

Step 2: Generate configuration

After creating the app, initialize the fly.toml configuration file:

fly launch

This will generate a fly.toml file where you can configure:

• App name and primary region
• Build settings (Dockerfile or buildpacks)
• HTTP service configuration and health checks
• VM size and scaling rules

fly launch --dockerfile apps/api/Dockerfile
fly deploy --dockerfile apps/api/Dockerfile

Step 3: Deploy

Once configured, deploy your application:

fly deploy

Verify

• Set any required secrets: fly secrets set KEY=value
• Verify the app is running: fly status
• Check logs: fly logs

Troubleshooting

• Deploy fails with build errors: Confirm Dockerfile path and local build success.
• App starts but health checks fail: Verify exposed port and health check settings in fly.toml.
• Wrong region selected: Update primary region and redeploy.