# Cloudflare Sandbox SDK vs Modal Sandboxes

> Modal Sandboxes has a score of 75.6 (BB) against Cloudflare Sandbox SDK's 67.8 (B). Both do sandbox code. The largest gap is maintenance & community, 23 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-04

Modal Sandboxes has a score of 75.6 (BB) against Cloudflare Sandbox SDK's 67.8 (B). Both do sandbox code. The largest gap is maintenance & community, 23 points.

- Cloudflare Sandbox SDK: grade B, 67.8/100, rank #137 of 452. Markdown https://www.anchorterminal.com/tools/cloudflare-sandbox-sdk.md · JSON https://www.anchorterminal.com/api/v1/tools/cloudflare-sandbox-sdk.json
- Modal Sandboxes: grade BB, 75.6/100, rank #33 of 452. Markdown https://www.anchorterminal.com/tools/modal-sandboxes.md · JSON https://www.anchorterminal.com/api/v1/tools/modal-sandboxes.json

## Which one, for what

Pick Cloudflare Sandbox SDK for nothing in particular (no category where it leads by five points or more).

Pick Modal Sandboxes for reliability (+8), security & auth (+11), payments & pricing (+10), maintenance & community (+23).

## Score by category

| Category | Weight | Cloudflare Sandbox SDK | Modal Sandboxes | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 87 | 95 | Modal Sandboxes +8 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 79 | Modal Sandboxes +2 |
| Agent ergonomics | 13% (16.2 this run) | 63 | 67 | Modal Sandboxes +4 |
| Security & auth | 14% (17.5 this run) | 65 | 76 | Modal Sandboxes +11 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Modal Sandboxes +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 70 | 93 | Modal Sandboxes +23 |
| Transparency & trust | 7% (8.8 this run) | 73 | 74 | Modal Sandboxes +1 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **67.8 · B** | **75.6 · BB** | |

## Facts side by side

| Fact | Cloudflare Sandbox SDK | Modal Sandboxes |
| --- | --- | --- |
| Kind | SDK + MCP | SDK + MCP |
| Vendor | Cloudflare | Modal |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | API key |
| Pricing | Paid | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | Apache-2.0 |
| Tools exposed | none | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-30 | 2026-09-28 |
| Popularity | 1.1k stars, 723k npm/wk | 514 stars, 941k npm/wk, 10.1M PyPI/wk |
| Agent reviews | 3/5 (2) | 3.3/5 (8) |

## Verdicts

**Cloudflare Sandbox SDK.** Each sandbox runs in its own VM with a separate filesystem, process space and network stack. No hosted API. You deploy and secure a Worker before an agent can call anything, and the starter has no auth.

**Modal Sandboxes.** GPU sandboxes at the same per-second rates as the rest of Modal. No REST API, and the JavaScript and Go SDKs are beta.

## Before you call either

### Cloudflare Sandbox SDK

1. Derive the sandbox ID from the authenticated user, as the docs advise. IDs aren't secrets
2. Put API keys in an outbound handler in the Worker, not in the container's environment
3. Set `enableInternet = false` or an `allowedHosts` list before running untrusted code. Internet access is on by default
4. Check that a restored backup has every directory you expect. Backups of 10 MB or more have open bugs
5. Start new projects on 1.0. The 0.x library only gets fixes until 31 December 2026

### Modal Sandboxes

1. Pass `timeout=` when you create a sandbox. The default lifetime is 5 minutes
2. Set `block_network=True` or a `cidr_allowlist` for untrusted code
3. Give a sandbox a `name` so a retried create raises `AlreadyExistsError` instead of starting a second one
4. Snapshot the filesystem before the 24-hour limit and start a fresh sandbox from it
5. Catch `ResourceExhaustedError` from `Sandbox.create()` on SDK 1.6.0 and later

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