Replit Docs

Replit Apps are configured with two files: the .replit and replit.nix. They affect how your Replit App behaves, from code execution to development tools and languages. These configuration files are hidden by default. Show them in your Replit App by selecting “Show hidden files” from the filetree menu.

`replit.nix` file

Replit uses Nix to manage packages and environments. The replit.nix file is used for: Specifying system dependencies: Define exactly what software packages your Replit App requires, managed through Nix, a package manager. Creating reproducible environments: Ensure your development environment is consistent and reproducible, ideal for collaborative projects and testing across multiple systems. You can manage Nix packages visually through the Dependencies tool. Learn more in the System Dependencies guide. To configure packages with the replit.nix file, you can list Nix packages in the deps array, prefixed with pkgs.. Any changes will be synced after your shell is reloaded.

{ pkgs }: {
  deps = [
    pkgs.nodejs-19_x
    pkgs.nodePackages.typescript-language-server
    pkgs.yarn
    pkgs.replitPackages.jest
  ];
}

`.replit` file

The .replit file controls your Replit App’s behavior. It uses the toml configuration format. Here are some of the key aspects that can be configured: Run command: Specify the command that executes when the Run button is selected. Each template has a default run command to allow code execution immediately. For more customized and complex apps, use Workflows. Language Server Protocol (LSP): Provides features like auto-complete, code navigation, code highlighting, and real-time linting and errors. Environment variables: Set and manage environment variables essential for your applications to run correctly. Dependencies and packages: Manage package installations and configurations directly through the .replit file, ensuring your Replit App has all the necessary tools ready upon startup. You can manage dependencies visually through the Dependencies tool. Learn more in the System Modules guide. For Python applications, the default .replit file looks like:

entrypoint = "main.py"
modules = ["python-3.10:v18-20230807-322e88b"]

[nix]
channel = "stable-23_05"

[unitTest]
language = "python3"

[gitHubImport]
requiredFiles = [".replit", "replit.nix"]

[deployment]
run = ["python3", "main.py"]
deploymentTarget = "cloudrun"

The following table provides a view of each setting within the .replit file, explaining what each configuration does and its impact on the Replit App environment.

Configuration key	Value/Example	Description
`entrypoint`	`main.py`	Specifies the main file to be executed and displayed by default when the editor is opened. You can rename the file name based on your application.
`modules`	`["python-3.10:v18-20230807-322e88b"]`	Defines specific versions of programming languages or other major dependencies supported by Replit.
`[nix]`		Specifies settings for using Nix, a package manager, to manage system dependencies. Refer to Dependency Management document for more information.
`channel`	`stable-23_05`	Indicates the Nix channel to use, which affects the versions of system dependencies available.
`packages`	`["cowsay", "htop"]`	Specifies some Nix packages to install. For more fine-grained control you can also use `replit.nix`.
`[unitTest]`		Configures settings related to unit testing within the Replit App.
`language`	`python3`	Specifies the language used for unit testing, indicating that Python 3 is used for writing tests.
`[gitHubImport]`		Settings that affect how projects are imported from GitHub, specifically which files must be included.
`requiredFiles`	`[".replit", "replit.nix"]`	Lists the files that must be present when importing the project to ensure it functions correctly.
`[deployment]`		Contains settings for deploying the application from the Replit App to a live environment.
`run`	`["python3", "main.py"]`	Command executed to start the application during deployment.
`deploymentTarget`	`cloudrun`	Specifies the deployment target platform for hosting the application.

Now that you have an idea of the default configurations of the .replit file use the next sections to understand how to configure basic and advanced settings for your Replit App.

Configuring basic settings

Entrypoint

This is the main file of your project. If you do not define a run property, entrypoint is the file that gets executed by the runtime.

entrypoint = "<file-name>.py"

`Run` command

The run property in the .replit file is a key feature that determines the initial command or series of commands executed when the Run button is selected in a Replit environment. The Run command can be specified either as a string representing the command to execute, or an array of strings representing the command and individual arguments to that command. Some common ways to configure the Run command:

Single command: This example shows how to pass single command to execute directly in the Replit App. With this in your .replit file, pressing the Run button will display a greeting in the Console pane: Example: run = "echo 'Hello, Replit!'"
Explicit arguments: In some situations it may be beneficial to be more explicit, avoiding the need for parsing quotes or shell interpolation rules. You can rewrite the above example to separate the arguments. Note, you no longer need both ' and ", since you are explicitly passing the greeting as the first and only argument to echo: Example: run = ["echo", "Hello, Replit!"]
Multiple commands: This example shows how to run multiple processes, such as a frontend and a backend, simultaneously. This could be useful if developing a python backend and a typescript frontend, where each server binds to a different port: Example: run = "python -m app & npm run start & wait"

Process management

While multiple commands can be simultaneously run with &, you may want a better experience distinguishing logs between services. You can add system dependencies like process-compose to better orchestrate multiple processes.

`Build` phase

For some languages or runtimes, there is a separate compilation phase before code can be run. This covers both compiled languages like TypeScript, Golang, or Java, or offering a parameter you can use to reset your environment, data, or configuration before the next run is invoked.

Compiling: In a TypeScript repository, you may find yourself needing to run tsc prior to executing your code. Example:

build = "tsc app.ts"
run = "node app.js"

Including environment variables

To supply environment variables to your service before execution, you can expand the run property into a table. This is a more involved change, and likely requires moving where your run = "..." property is located inside your .replit file. The following diff shows supplying the command by way of [run]’s args, as well as the variable NAME supplied in [run.env]:

-run = ["bash", "-c", "echo \"Hello, $NAME!\""]

 modules = ["nodejs-20"]

 hidden = [".pythonlibs"]

+# We need to move our new [run] down past all the
+# top-level properties that do not start with a `[`!
+[run]
+args = ["bash", "-c", "echo \"Hello, $NAME!\""]
+
+[run.env]
+NAME="Replit"

 [nix]
 channel = "stable-23_11"

Interactivity

Interactive programs can also be launched by way of the Run button, offering a way to distinguish your development environment from the terminal where your program is running. Consider the following tally script: Example

[run]
args = ["bash", "-c", """
count=0
while read -p "$PROMPT" -r next && [ -n "$next" ]; do
    count=$((count+next))
done
echo "The numbers you entered sum to $count!"
"""]

[run.env]
PROMPT = "Next number ([Enter] to end): "

Advanced configuration options

Explore the detailed configuration options available for your Replit App. You can customize your development environment, manage run commands, integrate language services, and handle dependencies.

Configuration	Key	Value/Example	Description
onBoot	`onBoot`	`onBoot = "npm install"`	Command that executes when the Replit App boots up.
compile	`compile`	(No default example)	Command that runs before the `run` command, used in compiled languages like C++.
language	`language`	`language = "javascript"`	Specifies the language during a GitHub import or when creating a Replit App.
entrypoint	`entrypoint`	`entrypoint = "index.js"`	Main file to run and display when opening the editor.
hidden	`hidden`	`hidden = [".config", "package-lock.json"]`	Files or folders to hide by default in the side file tree.
audio	`audio`	`audio = true`	Enables System-Wide Audio when set to `true`.

Notes about System-Wide Audio

When setting audio = true in your .replit file, you may need to run kill 1 in a shell to force the new setting to take effect. When running a graphical application, you will see a pair of headphones with a checkbox in the lower right of the Output pane. Due to browser restrictions, this will need to be enabled every time you refresh.

# Ensure this is at the top of your `.replit` file, outside of any `[`-bracketed section
audio = true

Packager configuration

Configuration	Key	Value/Example	Description
packager	`language`	`packager.language = "python3"`	Language used for package operations.
packager features	`guessImports`	`packager.features.guessImports = true`	Automatically guess packages to install prior to running the Replit App.
packager features	`packageSearch`	`packager.features.packageSearch = true`	Enables support for the packager when set to `true`.
packager features	`enabledForHosting`	`packager.features.enabledForHosting = false`	Sets whether hosting the Replit App requires running a package installation.
packager	`afterInstall`	`afterInstall = "echo 'package installed'"`	Command executed after a new package is installed via the packager.
packager	`ignoredPaths`	`ignoredPaths = [".git"]`	Paths to ignore while attempting to guess packages.
packager	`ignoredPackages`	`ignoredPackages = ["twitter", "discord"]`	Modules should never attempt to guess a package during installation.

Example `.replit` configuration for packager configuration

# Define the language for the Replit App
packager.language = "python3"

# Enable features for automatic package management
[packager.features]
guessImports = true
packageSearch = true
enabledForHosting = false

# Command to run after each package installation
packager.afterInstall = "echo 'Package installed successfully'"

# Define paths and packages that should be ignored by the package manager
packager.ignoredPaths = [".git", "node_modules"]
packager.ignoredPackages = ["twitter", "discord"]

# Additional deployment settings
[deployment]
run = ["python3", "app.py"]

Deployment configuration

Configuration	Key	Value/Example	Description
deployment	`run`	`deployment.run = "npm start"`	Command that executes when a Deployment container starts.
deployment	`build`	`deployment.build = "npm run build"`	Command that executes before running a Deployment.
deployment	`ignorePorts`	`deployment.ignorePorts = true`	If `true`, deployment success doesn’t require an open port check.

Example `.replit` configuration for deployment configuration

# Specifies the main entry point for the project
entrypoint = "app.js"

# Configuration settings for deploying the application
[deployment]
run = "npm start"
build = "npm run build"
ignorePorts = true

Interpreter configuration has been deprecated and is no longer available in Replit. Instead, you are encouraged to use the Run commands to configure how scripts and applications are executed within your Replit App environment.

Port configuration

Configuration	Key	Value/Example	Description
ports	`localPort`	`localPort = 3000`	Port that Replit binds to an external port.
ports	`externalPort`	`externalPort = 80`	Publicly accessible port linked to the `localPort`.

Example `.replit` configuration file for managing ports

# Networking configuration to expose your application on specific ports
[[ports]]
localPort = 3000
externalPort = 80

Accessing Replit App environment metadata

Node.js

To access all environment variables: console.log(process.env); To access a single variable (REPL_SLUG): console.log(process.env.REPL_SLUG);

Python

To access all environment variables:

import os
print(os.environ)

To access a single variable (REPL_SLUG):

import os
variable = os.environ.get('REPL_SLUG')
print(variable)

Rust

To access all environment variables:

use std::env;
fn main() {
    for (key, value) in env::vars() {
        println!("{}: {}", key, value);
    }
}

To access a single variable (REPL_SLUG):

use std::env;
fn main() {
    let variable = env::var("REPL_SLUG").unwrap();
    println!("{}", variable);
}

Environment variables

Following are the environment variables accessible from within your Replit App:

key	description
`REPL_OWNER`	The username of the owner of the Replit App. If your Replit App is text-based and has no webserver, `REPL_OWNER` will reflect the value of the current user accessing the Replit App
`REPL_ID`	The unique UUID string of your Replit App
`HOME`	The home path of your Replit App
`system`	The operating system running on your Replit App
`LANG`	Sets the language and character encoding for your Replit App, affecting how text is processed and displayed
`REPL_IMAGE`	The docker image that corresponds to your Replit App
`REPL_LANGUAGE`	The programming language configured for your Replit App, used to determine the runtime environment and tooling
`REPL_PUBKEYS`	A stringified JSON object containing different public API keys
`REPL_SLUG`	A simplified, machine-readable version of the name of the Replit App, suitable for use in URLs and file names
`PRYBAR_FILE`	The main/entrypoint file of your Replit App
`REPLIT_DEV_DOMAIN`	Provides the `replit.dev` URL for your Replit App in the Project Editor. Note that this environment variable is not available in Deployments

​replit.nix file

​.replit file

​Configuring basic settings

​Entrypoint

​Run command

​Process management

​Build phase

​Including environment variables

​Interactivity

​Advanced configuration options

​Notes about System-Wide Audio

​Packager configuration

​Example .replit configuration for packager configuration

​Deployment configuration

​Example .replit configuration for deployment configuration

​Port configuration

​Example .replit configuration file for managing ports

​Accessing Replit App environment metadata

​Node.js

​Python

​Rust

​Environment variables

`replit.nix` file

`.replit` file

Configuring basic settings

Entrypoint

`Run` command

Process management

`Build` phase

Including environment variables

Interactivity

Advanced configuration options

Notes about System-Wide Audio

Packager configuration

Example `.replit` configuration for packager configuration

Deployment configuration

Example `.replit` configuration for deployment configuration

Port configuration

Example `.replit` configuration file for managing ports

Accessing Replit App environment metadata

Node.js

Python

Rust

Environment variables