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Elixir & Phoenix: Scalable Backend Development · Lesson

Phoenix Project Setup and Structure

Create a new Phoenix project, understand its directory structure, and explore core components like routers and controllers.

Phoenix Project Setup and Structure is a free Elixir & Phoenix: Scalable Backend Development lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Elixir & Phoenix: Scalable Backend Development learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Welcome to Phoenix!

Hello! In this lesson, we'll begin our journey with Phoenix, Elixir's powerful web framework. Phoenix helps you build robust, high-performance web applications and APIs.

It leverages the speed and fault-tolerance of the Erlang Virtual Machine (BEAM) through Elixir, making it ideal for real-time features and concurrent systems.

Why Choose Phoenix?

Phoenix combines the elegance of Elixir with the reliability of Erlang/OTP. This means your applications can handle many concurrent users with low latency and are highly resilient to failures.

It's a fantastic choice for building anything from simple websites to complex real-time applications like chat rooms or live dashboards.

Setup Your Environment

Before we create a Phoenix project, ensure you have Elixir and Erlang installed on your system. You can check your versions using the commands below.

If you don't have them, consider using asdf for easy installation and version management.

elixir -v
mix -v

Generating a New Project

The easiest way to start a new Phoenix project is by using the mix phx.new command. This command sets up a new application with all the necessary files and dependencies.

Let's create our first project, named hello_phoenix:

mix phx.new hello_phoenix

Understanding Project Structure

After running mix phx.new hello_phoenix, a new directory named hello_phoenix is created. Inside, you'll find a well-organized set of folders and files.

This structure helps keep your code modular and maintainable as your application grows.

Key Project Folders

Let's look at some of the top-level directories:

  • assets/: Contains your frontend files like CSS, JavaScript, and images.
  • config/: Holds configuration files for different environments (development, test, production).
  • priv/: Stores private application resources, such as database migrations and static files not served directly.

`lib/` - Your Application Code

The lib/ directory is the heart of your Elixir application. For Phoenix projects, it usually contains two main sub-directories:

  • lib/hello_phoenix/: Your core application logic and business rules.
  • lib/hello_phoenix_web/: Web-specific components like controllers, views, and routers.

This separation helps keep your web interface distinct from your core logic.

hello_phoenix/
├── lib/
│   ├── hello_phoenix/
│   └── hello_phoenix_web/

Introducing the Router

Inside lib/hello_phoenix_web/, you'll find router.ex. The router is like the traffic cop of your web application.

It defines how incoming web requests (like visiting a URL) are mapped to specific actions within your application, typically handled by controllers.

# lib/hello_phoenix_web/router.ex
defmodule HelloPhoenixWeb.Router do
  use HelloPhoenixWeb, :router

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    plug :put_root_layout, {HelloPhoenixWeb.LayoutView, :root}
    plug :protect_from_forgery
    plug :put_secure_browser_headers
  end

  scope "/", HelloPhoenixWeb do
    pipe_through :browser

    get "/", PageController, :index
  end
end

Running Your Phoenix App

After generating your project and installing dependencies (mix deps.get), you can start the development server. This compiles your code and makes your application accessible in your browser, usually at localhost:4000.

Navigate into your project directory first!

cd hello_phoenix
mix phx.server

Quick Check: Project Structure

The mix phx.new command creates a standard Phoenix project. Which directory is typically used for frontend assets like CSS and JavaScript?

Lesson Summary

Great job! You've successfully created your first Phoenix project using mix phx.new. We explored the basic directory structure, including assets/, config/, lib/, and priv/.

You now have an understanding of where your core application logic lives (lib/hello_phoenix) and where web-specific components reside (lib/hello_phoenix_web), including the crucial router.ex. Next, we'll dive deeper into how routing works and how controllers handle requests!

Frequently asked questions

Is the “Phoenix Project Setup and Structure” lesson free?

Yes — the full text of “Phoenix Project Setup and Structure” is free to read here on the web, and the Elixir & Phoenix: Scalable Backend Development course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Elixir & Phoenix: Scalable Backend Development course, upgrade to CoddyKit PRO.

What will I learn in “Phoenix Project Setup and Structure”?

Create a new Phoenix project, understand its directory structure, and explore core components like routers and controllers. You practise Elixir & Phoenix: Scalable Backend Development with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Elixir & Phoenix: Scalable Backend Development?

No prior experience is required. Elixir & Phoenix: Scalable Backend Development on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Phoenix Project Setup and Structure” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Elixir & Phoenix: Scalable Backend Development lesson?

Yes. Every Elixir & Phoenix: Scalable Backend Development lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Phoenix Project Setup and Structure
  2. Routing, Controllers, and Plugs
  3. Views, Templates, and LiveView Basics
  4. Real-Time Features with Phoenix Channels
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