How to use multiple languages in Replit

Replit hides its configuration files by default. To edit them, click the three-dot menu at the top of the file tree panel on the left and select Show hidden files. This reveals the .replit and replit.nix files in your project root. These two files control your entire environment: .replit defines how your project runs, and replit.nix defines what system packages are available. You will edit both to set up multi-language support.

Open the replit.nix file and add the language packages you need to the deps array. Each package follows the pkgs.packageName format. Search for exact package names at search.nixos.org/packages. For example, to use both Python 3.11 and Node.js 20 with TypeScript support, add both runtimes and their associated language servers. After saving the file, run exit in the Shell to restart the environment and load the new packages.

1{ pkgs }: {
2  deps = [
3    pkgs.nodejs-20_x
4    pkgs.python311
5    pkgs.nodePackages.typescript-language-server
6    pkgs.python311Packages.python-lsp-server
7    pkgs.go_1_21
8  ];
9}

Open the .replit file and set the entrypoint and run command for your primary language. The entrypoint tells the editor which file to open by default, and the run command defines what happens when you click the Run button. If your main application is a Python backend, point run to your Python entry file. You can change this later or run secondary languages from the Shell.

1entrypoint = "main.py"
2run = ["python3", "main.py"]
3
4[nix]
5channel = "stable-24_05"
6
7[[ports]]
8localPort = 3000
9externalPort = 80

To run a Python backend and a Node.js frontend at the same time, use the ampersand operator in your run command to launch both as background processes. The wait command at the end keeps the parent process alive so both services stay running. Alternatively, open two Shell instances from the Tools dock and run each process in its own Shell tab for better log separation.

1# In .replit file, run both processes:
2run = "python3 api/server.py & cd frontend && npm start & wait"
3
4# Or run them in separate Shell tabs:
5# Shell 1: python3 api/server.py
6# Shell 2: cd frontend && npm start

Open the Shell and install packages for each language using its native package manager. Use pip install for Python, npm install for Node.js, and go mod tidy for Go. Each package manager stores dependencies in its own standard location: requirements.txt or pyproject.toml for Python, package.json for Node.js, and go.mod for Go. This keeps dependencies isolated by language even within the same project directory.

1# Python dependencies
2pip install flask requests
3pip freeze > requirements.txt
4
5# Node.js dependencies
6cd frontend
7npm install express react
8cd ..
9
10# Go dependencies
11cd services
12go mod init myapp/services
13go get github.com/gin-gonic/gin
14cd ..

Create a clear directory structure that separates each language's code. A common pattern is to have top-level folders for each service or language: api/ for your Python backend, frontend/ for your Node.js app, and scripts/ for any shell or utility scripts. Place shared configuration at the root. This structure makes it obvious which language each component uses and prevents package manager conflicts.

1# Recommended project structure:
2# .
3# ├── .replit          (run configuration)
4# ├── replit.nix       (system packages)
5# ├── api/
6# │   ├── server.py
7# │   ├── requirements.txt
8# │   └── routes/
9# ├── frontend/
10# │   ├── package.json
11# │   ├── src/
12# │   └── public/
13# └── scripts/
14#     └── seed_db.sh