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Modal Sandboxes

Answer in brief

Sandboxes on Modal’s serverless compute platform for running untrusted code at very high scale, with GPUs, snapshots and tunnels. The best fit when scale or GPUs matter most, especially for teams already on Modal.

By the Agent Sandboxes editors · Updated

Overview

Modal is a serverless compute platform for Python-heavy AI workloads, and its Sandboxes product exposes the same infrastructure for running untrusted code. Its strengths are scale — Modal says its scheduler is tested with over a million concurrent sandboxes — and GPUs, which are available in sandboxes at the same rates as the rest of the platform.

Isolation is gVisor by default, with a VM option. Snapshots (filesystem, directory and alpha memory snapshots) support fast restore and forking, which suits reinforcement learning and evaluation pipelines.

Notable

  • Raised a $750M Series D led by Accel at a $15.75B valuation in October 2026.
  • Says its scheduler is tested with over 1 million concurrent sandboxes.
  • Lists Cognition, Linear and Ramp among sandbox customers.

Modal Sandboxes specifications

AttributeDetails
IsolationgVisor by default, or VMs with their own Linux kernel; GPU sandboxes use gVisor
DeploymentHosted platform
Open sourceNo (Client SDK Apache-2.0)
SDKs and interfacesPython, JavaScript/TypeScript, Go
Cold start (vendor claim)Sub-second, including for large custom images (vendor claim)
Max session length5 minutes default, configurable up to 24 hours; snapshots carry state beyond that
PersistenceFilesystem snapshots, directory snapshots, memory snapshots (alpha) and Modal Volumes
GPUYes — Modal’s full GPU range (T4 to B300) at standard per-second rates, e.g. H100 $0.001097/s
NetworkingOutbound open by default; block all, CIDR allowlists or domain allowlists (beta), updatable at runtime; encrypted tunnels with public URLs and connect tokens
PricingPer second at sandbox (non-preemptible) rates: $0.00003942 per physical core-second (1 core = 2 vCPU) + $0.00000667 per GiB-second; GPUs at standard rates. Team plan $250/month
Free tier$30/month credits on Starter ($100/month on Team)
ComplianceSOC 2 on all plans; HIPAA on Enterprise
RegionsRegion selection available at a price multiplier

Facts from Modal Sandboxes’s public documentation, verified November 8, 2026. Performance numbers are vendor claims.

Strengths and trade-offs

Strengths

  • You need very high concurrency (RL, evals, batch agents)
  • You need GPUs inside the sandbox
  • You already use Modal for inference or training
  • You want Go as well as Python and TypeScript SDKs

Trade-offs

  • Sandbox compute billed at roughly 3x Modal’s standard list rates
  • Not open source and no documented BYOC
  • gVisor by default rather than microVMs

Best for: High-concurrency and GPU-backed sandboxes — RL rollouts, evals and coding agents at scale.

Where Modal Sandboxes ranks

How Modal Sandboxes compares

SandboxIsolationOpen sourceSelf-host / BYOCCold start (vendor)Max sessionSnapshots / pauseGPUSDKs
Modal SandboxesgVisor or VMNoNo / Not documented<1 sUp to 24 hYes / YesYesPython, JavaScript/TypeScript, Go
E2BFirecracker microVMYesYes / YesNot documented1 h / 24 h (Pro)Yes / YesNoPython, JavaScript/TypeScript
DaytonaContainers or VMsNoNot documented / Yes<90 msUnlimitedYes / YesYesPython, TypeScript, Ruby, Go, Java
Beam SandboxesgVisorYesYes / Yes~0.5 sConfigurableYes / YesYesPython, TypeScript
Northflank SandboxesCloud Hypervisor microVMNoNo / Yes<1 sUnlimitedNot documented / YesYesJavaScript/TypeScript, Python
Morph CloudVMNoNo / Not documented<250 ms (restore)ConfigurableYes / YesNot documentedPython, TypeScript

Head-to-head: E2B vs Modal Sandboxes · Daytona vs Modal Sandboxes · Modal Sandboxes vs Vercel Sandbox · Modal Sandboxes vs Cloudflare Sandbox SDK · Modal Sandboxes vs Fly.io Sprites · Northflank Sandboxes vs Modal Sandboxes · Beam Sandboxes vs Modal Sandboxes

See all Modal Sandboxes alternatives →

Frequently asked questions

What is Modal Sandboxes?
Sandboxes on Modal’s serverless compute platform for running untrusted code at very high scale, with GPUs, snapshots and tunnels. The best fit when scale or GPUs matter most, especially for teams already on Modal.
How does Modal Sandboxes isolate code?
Modal Sandboxes documents its isolation as: gVisor by default, or VMs with their own Linux kernel; GPU sandboxes use gVisor.
Is Modal Sandboxes open source?
No, Modal Sandboxes is not open source.
How much does Modal Sandboxes cost?
Per second at sandbox (non-preemptible) rates: $0.00003942 per physical core-second (1 core = 2 vCPU) + $0.00000667 per GiB-second; GPUs at standard rates. Team plan $250/month Check the official pricing page for current rates.
What are the best Modal Sandboxes alternatives?
Common alternatives include E2B, Daytona, Beam Sandboxes, Northflank Sandboxes, Morph Cloud. See Modal Sandboxes alternatives for a full comparison.

Sources

  1. modal.com/use-cases/sandboxes
  2. modal.com/pricing
  3. modal.com/docs/guide/sandbox
  4. modal.com/docs/guide/sandbox-networking
  5. modal.com/docs/guide/sandbox-snapshots
  6. pillsburylaw.com/en/news-and-insights/pillsbury-advises-modal-labs-on-750-million-financing.html

Cite this page

Agent Sandboxes. (2026). Modal Sandboxes. agentsandboxes.org. Last reviewed November 8, 2026. https://agentsandboxes.org/sandboxes/modal/

Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.