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Modal Sandboxes

Modal Labs
closed / Overall score: 3.4

Modal Sandboxes runs untrusted or agent-generated code in gVisor-isolated containers on Modal's serverless cloud, created at runtime from the Python, JavaScript or Go SDK. A sandbox can be built from an arbitrary container image, looked up later by name, given GPUs, and held open for anything from the five-minute default to twenty-four hours. Compute is billed by the core-second.

Modal bills Sandbox compute at a separate rate from its Function compute, so the plan tiers on the pricing page describe the surrounding platform rather than the sandbox itself.

Openness

1 high confidence
1.0
license
Proprietary
source
closed
service
proprietary Modal managed cloud (no self-host of the gVisor execution plane)
open-part
client SDK only (modal Python/JS client libraries)
pricing
pay-as-you-go usage, free starter credits

Modal Sandboxes is a closed managed service: the client SDK is open, but the execution substrate is a proprietary cloud with no self-host option, so an open client over a closed runtime does not make this open core. Unlike E2B, which ships self-hostable infrastructure, Modal does not.

  • https://modal.com/docs/guide/sandbox recorded 2026-06-04

    Sandboxes = secure containers for untrusted agent code, driven via Modal SDK

  • https://modal.com/docs/guide/sandbox recorded 2026-08-13

    Redirects to /docs/guide/sandboxes. Sandboxes are still "secure containers for executing untrusted user or agent code on Modal", created only through the Python, JavaScript or Go SDK against Modal's service; no runtime is distributed to run elsewhere.

  • https://modal.com/docs/guide/sandboxes recorded 2026-09-29

    Sandboxes guide describes "secure containers for executing untrusted user or agent code on Modal" created through the SDK; searched the body for self-host, on-prem and open source: none.

  • https://modal.com/legal/terms recorded 2026-09-29

    Modal Terms of Service bar customers from attempts to "reverse engineer, decompile, disassemble, or" discover the "algorithms of the Service or any software used to provide or make" it available, and name only the modal-client SDK as "available under open source licensing terms", adding "that the Modal Tools are not part of the Service".

  • https://modal.com/pricing recorded 2026-09-29

    Modal plan pricing page, with a section headed "Modal Sandbox + Notebooks Pricing", meters Starter, Team and Enterprise plans against Modal compute; searched the body for self-host, on-prem, open source and license: none.

  • https://raw.githubusercontent.com/modal-labs/modal-client/main/LICENSE recorded 2026-09-29

    The modal-client repository LICENSE file is the "Apache License" text, "TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION", covering the client SDK only.

Adoption

3 low confidence
3.0

Modal publishes no user or usage count for Sandboxes specifically. Its nearest disclosed figure is platform-wide -- a count of Modal teams overall, naming Lovable and Quora as production users running untrusted code -- so the level reflects reported multi-customer traction for the platform rather than a measured figure for the sandbox feature itself.

Capability

4 medium confidence
4.0

Modal Sandboxes isolate each container with gVisor's user-space kernel and support arbitrary custom images, named lookup, GPUs, and sessions from a five-minute default up to 24 hours. That isolation is a step below the microVM platforms, such as Firecracker, that lead the category, and independent ComputeSDK benchmarks place Modal's start-up speed mid-field.

Verified 2026-09-29