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Before You Start

You’ll need:
  • Python - we recommend 3.11
  • A fal account (sign up is free)

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Step 1: Install the CLI

pip install fal

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Step 2: Authenticate

Get your API key from the fal dashboard and authenticate: 
fal auth login
This opens your browser to authenticate with fal. Once complete, your credentials are saved locally.

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Step 3: Create Your First App

Create a file called hello_world.py with this simple app: 
import fal

class MyApp(fal.App):
    @fal.endpoint("/")
    def run(self) -> dict:
        return {"message": "Hello, World!"}
That’s it! This is the simplest possible fal app - it just returns a message when called.

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Step 4: Test Your App Locally

First, run your app locally to test it: 
fal run hello_world.py::MyApp
This command:
  • Starts your app as a service
  • Provides two URLs for interaction: a direct HTTP proxy and a web playground
  • Allows you to test your app without authentication while fal run is active
As soon as the app is ready, you’ll see a message like this: 
INFO:     Application startup complete.
Now you can test your app by making HTTP requests to the provided URL: 
curl $FAL_RUN_URL -H 'content-type: application/json' -H 'accept: application/json, */*;q=0.5' -d '{}'
You should see: 
{"message": "Hello, World!"}
Alternatively, you can use the auto-generated playground web UI to interact with your app through a browser interface.

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Step 5: Deploy Your App (Optional)

Once you’re satisfied, deploy it to create a persistent URL: 
fal deploy hello_world.py::MyApp
This command:
  • Deploys your app as a serverless function
  • Makes your app available for requests, with runners managed automatically based on demand
  • Returns a unique persistent URL for your deployed app

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What Just Happened?

🎉 Congratulations! You’ve successfully:
  1. Created a fal app: Built the simplest possible serverless function
  2. Tested locally: Ran your app and called it with an HTTP request
  3. Deployed to the cloud: Made your app accessible via REST API (if you chose to deploy)
The beauty of this workflow is you can test and iterate locally before deploying to production.

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Next Steps

Now that you have a working app, you can: