Introduction

Last updated: June 1, 2026

What WebSandbox is, why it exists, and how it differs from every other development environment you have used.

What is WebSandbox?

WebSandbox provides two distinct environments depending on your project needs:

• Instant Projects — a fully in-browser environment using WebContainers technology. Code executes locally inside a secure WASM-based OS sandboxed by the browser itself. This means zero cold-start latency and true privacy (your code never leaves your machine unless pushed to a remote).
• Cloud Servers — powerful, VM-backed environments running on our cloud infrastructure. Ideal for large monorepos, projects requiring native binaries, or complex setups that exceed browser memory limits.

The Problem We Solve

Setting up a local development environment is one of the most friction-heavy parts of software engineering. Between nvm install, conflicting global packages, missing native dependencies, and OS-specific quirks, hours can disappear before a single line of product code is written.

Existing cloud IDEs solve the setup problem but introduce new ones: persistent VMs are expensive, they have cold-start delays, network dependency for every keypress, and they require trusting a third party with your source code at rest.

WebSandbox eliminates both categories of friction:

• Instant setup — environments are pre-configured and ready in seconds.
• Flexibility — choose in-browser execution (Instant Projects) for speed and privacy, or robust VMs (Cloud Servers) for heavy lifting.
• No vendor lock-in — export your code or push to git at any time.

How it Works at a Glance

When you open a WebSandbox workspace, the boot sequence depends on the environment type:

Instant Projects (Browser-based)

1. Service Worker registers and intercepts all localhost:PORT requests.
2. Your project files are loaded from IndexedDB and mounted into the virtual file system.
3. The WebContainer boots, installs dependencies, and starts the dev server in the browser process.
4. The preview pane renders your running application via a sandboxed iframe.

Cloud Servers (VM-based)

1. A dedicated VM or container is provisioned and your workspace volume is mounted.
2. VSCode Server initializes on the remote instance.
3. The terminal and dev server start remotely, and traffic is port-forwarded securely to your browser preview pane.

A Proprietary Platform

WebSandbox is a proprietary product built and maintained by the WebSandbox team. The platform, its engine, persistence layer, and editor integrations are not open source. This documentation covers the public-facing API, product behaviour, and integration guides. Internal implementation details are shared selectively through our engineering blog.

Next Steps

Ready to dive in? Head to the Quick Start guide to create your first workspace in under 60 seconds, or explore the Core Concepts section to understand the architecture in depth.