Local development

This Quick Start scenario assumes that you are installing the DFINITY Canister SDK for the first time and want to run a canister smart contract in a local canister execution environment instead of deploying it to the Internet Computer blockchain.

To get started, let’s build and deploy a simple Hello canister that has just one function—called greet. The greet function accepts one text argument and returns the result with a greeting similar to Hello, everyone! in a terminal if you run the canister using the command-line or in an HTML page if you access the canister in a browser.

Before you begin

Before you download and install this release of the DFINITY Canister SDK, verify the following:

You have an internet connection and access to a shell terminal on your local macOS or Linux computer.

Currently, the DFINITY Canister SDK only runs on computers with a macOS or Linux operating system.
You have node.js installed if you want to include the default template files for front-end development in your project.

This tutorial assumes you know how to perform common tasks—like opening a terminal and running commands—on your computer. If you aren’t sure how to open a new terminal shell on your local computer or how to install node.js, see Preliminary steps for newcomers. If you are comfortable meeting the prerequisites without instructions, continue to Download and install.

Download and install

You can download the latest version of the DFINITY Canister Software Development Kit (SDK) directly from within a terminal shell on your local computer.

To download and install:

Open a terminal shell on your local computer.

For example, open Applications, Utilities, then double-click Terminal or press ⌘+spacebar to open Search, then type terminal.
Download and install the DFINITY Canister SDK package by running the following command:
```
sh -ci "$(curl -fsSL https://sdk.dfinity.org/install.sh)"
```
This command prompts you to read and accept the license agreement before installing the DFINITY execution command-line interface (CLI) and its dependencies on your local computer.
Type y and press Return to continue with the installation.

The command displays information about the components being installed on the local computer.

Verify the SDK is ready to use

If the installation script runs without any errors, everything you need to start developing programs that run on the Internet Computer blockchain will be available on your local computer.

To verify the SDK is ready to use:

Open a terminal shell on your local computer, if you don’t already have one open.
Check that you have the DFINITY execution command-line interface (CLI) installed and the dfx executable is available in your PATH by running the following command:
```
dfx --version
```
The command displays version information for the dfx command-line executable similar to the following:
```
dfx 0.9.0
```
Preview usage information for the other dfx command-line sub-commands by running the following command:
```
dfx --help
```
The command displays usage information for the dfx parent command and its subcommands.

Create a new project

Dapps on the Internet Computer start as projects. You create projects using the dfx parent command and its subcommands.

For this tutorial, we’ll start with the default sample dapp to illustrate creating dapp using the starter files in a project. When you create a new project, the dfx command-line interface adds a default project directory structure to your workspace. We cover the template files that make up a project directory in the Explore the default project tutorial.

To create a new project for your first application:

Open a terminal shell on your local computer, if you don’t already have one open.
Create a new project named hello by running the following command:
```
dfx new hello
```
The dfx new hello command creates a new hello project directory, template files, and a new hello Git repository for your project.

If you use a different project name instead of hello, make note of the name you used. You’ll need to use that project name in place of the hello project name throughout these instructions.
Change to your project directory by running the following command:
```
cd hello
```

Start the local deployment

Before you can build your first project, you need to connect to the local canister execution environment. As a best practice, this step requires you to have two terminal shells open, so that you can start and see canister execution operations in one terminal and manage your project in another.

To prepare the local canister execution environment:

Open a new second terminal window or tab on your local computer.
Navigate to the root directory for your project, if necessary.

You should now have two terminals open with your project directory as your current working directory in both terminals.
Start the local canister execution environment on your computer in your second terminal by running the following command:
```
dfx start
```
Depending on your platform and local security settings, you might see a warning displayed. If you are prompted to allow or deny incoming network connections, click Allow.
Leave the terminal window that displays canister execution operations open and switch your focus to the first terminal window where you created your new project.

You perform the remaining steps in the terminal that doesn’t display canister execution operations.

Register, build, and deploy the application

After you connect to the local canister execution environment you can register, build, and deploy your dapp locally.

To deploy your first dapp locally:

Check that you are still in the root directory for your project, if needed.
Ensure that node modules are available in your project directory, if needed, by running the following command:
```
npm install
```
For more information about this step, see Ensuring node is available in a project.

dfx deploy

The dfx deploy command output displays information about the operations it performs. For example, this step registers two identifiers—one for the hello main program and one for the hello_assets front-end user interface—and installation information similar to the following:

Creating a wallet canister on the local network.
The wallet canister on the "local" network for user "default" is "rwlgt-iiaaa-aaaaa-aaaaa-cai"
Deploying all canisters.
Creating canisters...
Creating canister "hello"...
"hello" canister created with canister id: "rrkah-fqaaa-aaaaa-aaaaq-cai"
Creating canister "hello_assets"...
"hello_assets" canister created with canister id: "ryjl3-tyaaa-aaaaa-aaaba-cai"
Building canisters...
Building frontend...
Installing canisters...
Creating UI canister on the local network.
The UI canister on the "local" network is "r7inp-6aaaa-aaaaa-aaabq-cai"
Installing code for canister hello, with canister_id rrkah-fqaaa-aaaaa-aaaaq-cai
Installing code for canister hello_assets, with canister_id ryjl3-tyaaa-aaaaa-aaaba-cai
Authorizing our identity (default) to the asset canister...
Uploading assets to asset canister...
  /index.html 1/1 (573 bytes)
  /index.html (gzip) 1/1 (342 bytes)
  /index.js 1/1 (605692 bytes)
  /index.js (gzip) 1/1 (143882 bytes)
  /main.css 1/1 (484 bytes)
  /main.css (gzip) 1/1 (263 bytes)
  /sample-asset.txt 1/1 (24 bytes)
  /logo.png 1/1 (25397 bytes)
  /index.js.map 1/1 (649485 bytes)
  /index.js.map (gzip) 1/1 (149014 bytes)
Deployed canisters.

If you created a project with a different name, however, your canister names will match your project name instead of hello and hello_assets.

You should also note that the first time you deploy, dfx creates a default identity and a local cycle wallet controlled by your default identity. A cycles wallet is a special type of canister that enables you to transfer cycles to other canisters.

To deploy this sample dapp locally, you don’t need to know anything about your default developer identity, using a cycles wallet, or managing cycles. We’ll cover these topics later, but for now, just note that these are created for you automatically.

Call the hello canister and the predefined greet function by running the following command:
```
dfx canister call hello greet everyone
```
Let’s take a closer look at this example command:
- The dfx canister call command requires you to specify a canister name and a method—or function—to call.
- hello specifies the name of the canister you want to call.
- greet specifies the name of the function you want to call in the hello canister.
- everyone is the text data type argument that you want to pass to the greet function.
Remember, however, that if you created a project with a different name, the canister name will match your project name and you’ll need to modify the command line to match the name you used instead of hello.
Verify the command displays the return value of the greet function.

For example:
```
("Hello, everyone!")
```

Test the dapp front-end

Now that you have verified that your dapp has been deployed and tested its operation using the command line, let’s verify that you can access the front-end using your web browser.

Start the development server with npm start
Open a browser.
Navigate to http://localhost:8080/

Navigating to this URL displays a simple HTML page with a sample asset image file, an input field, and a button. For example:

+ Sample HTML page

Type a greeting, then click Click Me to return the greeting.

For example:

Stop the local canister execution environment

After testing the application in the browser, you can stop the local canister execution environment so that it doesn’t continue running in the background.

To stop the local deployment:

In the terminal that displays the development server, press Control-C to interrupt the development server process.
In the terminal that displays canister execution operations, press Control-C to interrupt the local network process.
Stop the local canister execution environment running on your local computer by running the following command:
```
dfx stop
```

Next steps

This Quick Start touched on only a few key steps to introduce the basic workflow for developing dapps of your own. You can find more detailed examples and tutorials to help you learn about how to use Motoko and how to develop dapps to run on the Internet Computer blockchain throughout the documentation.

Here are some suggestions for where to go next:

Tutorials to explore building simple dapps using a local canister execution environment.
Convert ICP tokens to cycles if you have ICP tokens that you want to convert to cycles to enable you to deploy dapp to the Internet Computer blockchain.
On-chain deployment if you have cycles and are ready to deploy an application to the Internet Computer blockchain mainnet.
What is Candid? to learn how the Candid interface description language enables service interoperability and composability.
Motoko at-a-glance to learn about the features and syntax for using Motoko.