dfx start

Reference

Use the dfx start command to start a local development environment and web server processes. This command must be run before you can deploy canisters to the local development environment and test your dapps during development.

By default, all local dfx projects will use PocketIC to create this local development environment. You can run dfx start and dfx stop from any directory. See local server configuration and project-specific local networks below for exceptions.

Basic usage

dfx start [option] [flag]

Flags

You can use the following optional flags with the dfx start command.

Flag	Description
--background	Starts the local development environment and web server processes in the background and waits for a reply before returning to the shell.
--clean	Starts the local development environment and web server processes in a clean state by removing checkpoints from your project cache. You can use this flag to set your project cache to a new state when troubleshooting or debugging.
--enable-bitcoin	Enables Bitcoin integration.
--enable-canister-http	Deprecated and now enabled by default.
--pocketic	Runs PocketIC instead of the replica. PocketIC is the default if no flag is used.

Options

You can use the following option with the dfx start command.

Option	Description
--host host	Specifies the host interface IP address and port number to bind the frontend to. The default for the local shared network is 127.0.0.1:4943, while the default for a project-specific network is '127.0.0.1:8000'.
--bitcoin-node host:port	Specifies the address of a bitcoind node. Implies --enable-bitcoin.
--artificial-delay milliseconds	Specifies the delay that an update call should incur. Default: 600ms
--domain domain	A domain that can be served. Can be specified more than once. These are used for canister resolution [default: localhost]

Examples

You can start the local development environment and web server processes in the current shell by running the following command:

dfx start

If you start the local development environment in the current shell, you need to open a new terminal shell to run additional commands. Alternatively, you can start the local development environment in the background by running the following command:

dfx start --background

If you run the local development environment in the background, however, be sure to stop the local development environment before uninstalling or reinstalling the dfx execution environment by running the following command:

dfx stop

You can view the current process identifier (pid) for the local development environment process started by dfx by running the following command:

more .dfx/pid

Local server configuration

The shared local network

dfx start manages a PocketIC server that provides a local development environment. Running dfx deploy and other commands will manage canisters on this local network in the same way that dfx deploy --network ic deploys projects to the mainnet.

If run from outside a dfx project directory, or if dfx.json does not define the local network, then dfx start looks for the local network definition in $HOME/.config/dfx/networks.json. If this file does not exist or does not contain a definition for the local network, then dfx uses the following default definition:

{
  "local": {
    "bind": "127.0.0.1:4943",
    "type": "ephemeral"
  }
}

dfx stores data for the shared local network in one of the following locations, depending on your operating system:

• $HOME/.local/share/dfx/network/local (Linux)
• $HOME/Library/Application Support/org.dfinity.dfx/network/local (macOS)

Project-specific local networks

If dfx.json defines the local network, then dfx start will use this definition and store network data files under <project dir>/.dfx/network/local.

Note that for projects that define the local network in dfx.json, you can only run the dfx start and dfx stop commands from within the project directory structure. For example, if your project name is hello_world, your current working directory must be the hello_world top-level project directory or one of its subdirectories.