Concepts (25)

Last updated Sep 30, 2026 Note

This page documents Sandbox SDK 0.x for existing applications. For new applications, refer to Sandboxes. To move an existing application to @cloudflare/sandbox 1.0, refer to Migrate from Sandbox SDK 0.x.

These pages explain how the Sandbox SDK works, why it's designed the way it is, and the concepts you need to understand to use it effectively.

• Architecture - How the SDK is structured and why
• Sandbox lifecycle - Understanding sandbox states and behavior
• Container runtime - How code executes in isolated containers
• Session management - When and how to use sessions
• Preview URLs - How to expose sandboxed services on the public internet.
• Security model - Isolation, validation, and safety mechanisms
• Terminal connections - How browser terminal connections work
• Directory backups - Overlay restore, local extract, and cross-device renames

Related resources

• Tutorials - Learn by building complete applications
• How-to guides - Solve specific problems
• API reference - Technical details and method signatures

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description: Sandbox SDK 0.x combines Workers, Durable Objects, and Containers for secure code execution. title: Architecture image: https://developers.cloudflare.com/sandbox/sdk/concepts/architecture/og.png?v=fc9759f139bbeafd

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