How to manage packages in Replit

Open the Shell tab from the Tools dock on the left sidebar. For Node.js projects, use npm install followed by the package name. The --save flag (default in modern npm) records the package in your package.json under dependencies. Use --save-dev for packages needed only during development (testing frameworks, build tools). npm creates a node_modules directory and a package-lock.json file that locks exact package versions.

1# Install a production dependency
2npm install express
3
4# Install multiple packages at once
5npm install cors dotenv mongoose
6
7# Install a development dependency
8npm install --save-dev jest nodemon
9
10# Install a specific version
11npm install react@18.2.0

For Python projects, use pip install in the Shell. After installing all needed packages, run pip freeze to generate a requirements.txt file that lists exact versions. This file serves the same purpose as package-lock.json — it ensures every collaborator and deployment uses identical package versions. Always commit requirements.txt to your project.

1# Install a single package
2pip install flask
3
4# Install multiple packages
5pip install requests sqlalchemy flask-cors
6
7# Install a specific version
8pip install numpy==1.24.0
9
10# Save all installed packages to requirements.txt
11pip freeze > requirements.txt
12
13# Install from requirements.txt (for collaborators)
14pip install -r requirements.txt

Replit provides a graphical interface for installing packages. Open the Dependencies tool from the Tools dock (or search for 'Packages' in the search bar). Type a package name in the search field to find it, then click the install button. The GUI detects your project type (Node.js, Python, etc.) and uses the appropriate package manager behind the scenes. This is useful when you want to browse packages without memorizing exact names or when you are new to the command line.

Keeping packages updated prevents security vulnerabilities and ensures compatibility. Use npm update to update all packages to the latest versions allowed by your package.json version ranges. To remove a package you no longer need, use npm uninstall. For Python, use pip install --upgrade to update a specific package, and pip uninstall to remove one.

1# Node.js — update all packages
2npm update
3
4# Node.js — update a specific package
5npm install express@latest
6
7# Node.js — remove a package
8npm uninstall unused-package
9
10# Python — upgrade a package
11pip install --upgrade flask
12
13# Python — remove a package
14pip uninstall package-name
15
16# Python — regenerate requirements.txt after changes
17pip freeze > requirements.txt

Set the onBoot command in your .replit file so dependencies install automatically whenever the Repl starts. This is especially important for team projects where collaborators should not need to manually run install commands after opening the project. Open .replit and add the onBoot line. For projects using both npm and pip, chain the commands.

1# .replit file
2
3# Auto-install on startup
4onBoot = "npm install"
5
6# For Python projects:
7onBoot = "pip install -r requirements.txt"
8
9# For polyglot projects (both Node.js and Python):
10onBoot = "npm install && pip install -r requirements.txt"

Deployment builds run in a clean environment without pre-installed packages. You must include the install command in your [deployment] build step. Use npm ci (not npm install) for deployment builds because it installs exact versions from package-lock.json and is faster. Make sure package-lock.json or requirements.txt is committed to your project — without them, npm ci will fail.

1[deployment]
2build = ["sh", "-c", "npm ci && npm run build"]
3run = ["sh", "-c", "node dist/index.js"]
4deploymentTarget = "cloudrun"