Customize the sandbox container image with your own packages, tools, and configurations by extending the base runtime image.
The Sandbox SDK provides multiple Ubuntu-based image variants. Choose the one that fits your use case:
| Image | Tag suffix | Use case |
|---|---|---|
| Default | (none) | Lean image for JavaScript/TypeScript workloads |
| Python | -python |
Data science, ML, Python code execution |
| OpenCode | -opencode |
AI coding agents with OpenCode CLI |
# Default - lean, no Python
FROM docker.io/cloudflare/sandbox:0.7.0
# Python - includes Python 3.11 + data science packages
FROM docker.io/cloudflare/sandbox:0.7.0-python
# OpenCode - includes OpenCode CLI for AI coding
FROM docker.io/cloudflare/sandbox:0.7.0-opencodeThe default image is optimized for JavaScript and TypeScript workloads:
- Ubuntu 22.04 LTS base
- Node.js 20 LTS with npm
- Bun 1.x (JavaScript/TypeScript runtime)
- System utilities: curl, wget, git, jq, zip, unzip, file, procps, ca-certificates
The -python variant includes everything in the default image plus:
- Python 3.11 with pip and venv
- Pre-installed packages: matplotlib, numpy, pandas, ipython
The -opencode variant includes everything in the default image plus:
- OpenCode CLI ↗ for AI-powered coding agents
Create a Dockerfile in your project root:
FROM docker.io/cloudflare/sandbox:0.7.0-python
# Install additional Python packages
RUN pip install --no-cache-dir \
scikit-learn==1.3.0 \
tensorflow==2.13.0 \
transformers==4.30.0
# Install Node.js packages globally
RUN npm install -g typescript ts-node prettier
# Install system packages
RUN apt-get update && apt-get install -y \
postgresql-client \
redis-tools \
&& rm -rf /var/lib/apt/lists/*Update wrangler.jsonc to reference your Dockerfile:
{
"containers": [
{
"class_name": "Sandbox",
"image": "./Dockerfile",
},
],
}When you run wrangler dev or wrangler deploy, Wrangler automatically builds your Docker image and pushes it to Cloudflare's container registry. You don't need to manually build or publish images.
You can add sandbox capabilities to any Docker image using the standalone binary. This approach lets you use your existing images without depending on the Cloudflare base images:
FROM your-custom-image:tag
# Copy the sandbox binary from the official image
COPY --from=docker.io/cloudflare/sandbox:0.7.0 /container-server/sandbox /sandbox
ENTRYPOINT ["/sandbox"]The /sandbox binary starts the HTTP API server that enables SDK communication. You can optionally run your own startup command:
FROM node:20-slim
COPY --from=docker.io/cloudflare/sandbox:0.7.0 /container-server/sandbox /sandbox
# Copy your application
COPY . /app
WORKDIR /app
ENTRYPOINT ["/sandbox"]
CMD ["node", "server.js"]When using CMD, the sandbox binary runs your command as a child process with proper signal forwarding.
For more complex startup sequences, create a custom startup script:
FROM docker.io/cloudflare/sandbox:0.7.0-python
COPY my-app.js /workspace/my-app.js
COPY startup.sh /workspace/startup.sh
RUN chmod +x /workspace/startup.sh
CMD ["/workspace/startup.sh"]The base image already sets the correct ENTRYPOINT, so you only need to provide a CMD. The sandbox binary starts the HTTP API server, then spawns your CMD as a child process with proper signal forwarding.
#!/bin/bash
# Start your services in the background
node /workspace/my-app.js &
# Start additional services
redis-server --daemonize yes
until redis-cli ping; do sleep 1; done
# Keep the script running (the sandbox binary handles the API server)
wait- Image Management - Building and pushing images to Cloudflare's registry
- Wrangler configuration - Using custom images in wrangler.jsonc
- Docker documentation ↗ - Complete Dockerfile syntax
- Container concepts - Understanding the runtime environment