# InstaVM vs Modal Sandboxes

> Modal Sandboxes scores 66 (B) to InstaVM's 52.1 (D) for code sandboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/instavm-vs-modal-sandboxes
- Markdown: https://www.anchorterminal.com/compare/instavm-vs-modal-sandboxes.md (~5,250 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

Modal Sandboxes scores 66 (B) on agent readiness against InstaVM's 52.1 (D), and leads in 5 of 7 scored categories. InstaVM leads on reliability. Both do code sandboxes.

- InstaVM: grade D, 52.1/100, rank #1000 of 1510. Markdown https://www.anchorterminal.com/tools/instavm.md · JSON https://www.anchorterminal.com/api/v1/tools/instavm.json
- Modal Sandboxes: grade B, 66/100, rank #388 of 1510. Markdown https://www.anchorterminal.com/tools/modal-sandboxes.md · JSON https://www.anchorterminal.com/api/v1/tools/modal-sandboxes.json
- Best code execution sandboxes for AI agents: https://www.anchorterminal.com/best/code-sandboxes/index.md
- All 231 sandboxes comparisons: https://www.anchorterminal.com/compare/code-sandboxes/index.md
- Best GPU and serverless compute for AI workloads: https://www.anchorterminal.com/best/gpu-compute/index.md
- All 231 gpu compute comparisons: https://www.anchorterminal.com/compare/gpu-compute/index.md

## Which one, for what

### InstaVM (D)

Good for: Hosted microVM sandboxes with browser, desktop, OCI images, clones and public shares.

Ahead on:
- Reliability, 77 against 55

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: The free plan's $50 credit needs a card on file, and signup is in a browser

### Modal Sandboxes (B)

Good for: GPU work inside a sandbox, or agents already running on Modal.

Ahead on:
- Schema & documentation, 79 against 66
- Agent ergonomics, 67 against 51
- Security & auth, 79 against 41
- Maintenance & community, 93 against 35
- Transparency & trust, 78 against 57

Watch for: No REST API, and the JavaScript and Go SDKs are beta


## Why the edge

### Maintenance & community: Modal Sandboxes +58

- InstaVM (35): Closed service lines. The latest dated change found is Python SDK 0.26.1 on 15 July 2026, 114 days before the check, and the site changelog's only entry is 11 July (10). No SDK release in the 90 days to 6 November (0). A public changelog, support email and Discord, with no reply times seen (8 of 15). Official Python and JavaScript SDKs, last released in July and May 2026 (12 of 15). Package health of the SDK repositories was not read (5 of 10). Total 35.
- Modal Sandboxes (93): 1.6.3 on 2026-10-27 (30). 1.5.4 on 12 August, 1.5.5 on 28 August, 1.6.0 on 28 September, 1.6.1 on 3 October, 1.6.2 on 15 October and 1.6.3 on 27 October (20). 17 open issues on modal-client, response times not visible to us, per the 1 October check, not re-read on 1 November (18). The Python SDK is current, and the JavaScript and Go SDKs (both tagged 0.11.1, still beta) are in the same repository, read from a clone on 1 November (15). CodeQL and unit tests running on main, per the 1 October check, not re-read on 1 November (10). 30 + 20 + 18 + 15 + 10 = 93.

### Security & auth: Modal Sandboxes +38

- InstaVM (41): Plain API keys in a header, with API endpoints to create, list and delete them and no scopes found (20 of 30). Egress policies per session or VM can block all outbound traffic or allow named domains and CIDRs, but llms.txt describes full network access as the default (8 of 20). No guidance on untrusted output from executed code or browser sessions (3 of 15). An Audit Logs endpoint group exists in the API reference (10 of 15). No security.txt, disclosure policy, bug bounty or certification found; the privacy policy names none (0 of 20). Total 41.
- Modal Sandboxes (79): A token ID and secret pair per workspace, revocable, with an optional TTL through `modal token new --expires-in` since 1.6.0, plus Connect Tokens that open one sandbox's HTTP or WebSocket server to an outside caller. Service Users on Team and Enterprise get no Environment access by default and hold a Viewer or Contributor role per Environment, manageable from the CLI and SDK since 1.6.2. No token scoped to sandbox actions found (25). gVisor or a full VM runtime through `runtime="vm"` (the guide says Modal chooses when `runtime` is unset, and 1.6.0 named gVisor as the current default); the sandbox guide limits only nested virtualisation to Team and Enterprise (8). Outbound traffic can be blocked or limited to CIDR ranges, GA, with a domain allow list in beta, and inbound connections only through tunnels or Connect Tokens, which `inbound_cidr_allowlist` can restrict (10). Modal Secrets go into the sandbox's environment by default. Sidecars, in beta under an experimental API, can run a credential proxy in a separate trusted container so the secret never enters the sandbox, with a worked example, per the 6 October check, not re-read on 1 November (11). Audit logs on Enterprise only (10). SOC 2 Type 2, a private HackerOne bug bounty through security@modal.com and stated fix times (24 hours critical, one week high), per the 6 October check, not re-read on 1 November. No security.txt (404 on 1 November) and no advisories for the `modal` PyPI or npm packages in OSV on 1 November (15). 25 + 8 + 10 + 11 + 10 + 15 = 79.

### Reliability: InstaVM +22

- InstaVM (77): Hosted lines. Better Stack status page with four components, including the public API (20). The incident history shows no incidents for September, October or November 2026 (30). No rate limits with numbers found; Pro promises higher limits without figures (0). The Python SDK has a RateLimitError and an example retry loop with exponential backoff, but no 429 or Retry-After is documented, and there is no idempotency guidance (7 of 15). The terms commit to 99.9% monthly uptime with service credits, and Pro lists 99.9% (10). No beta or preview label on the API (10). Total 77.
- Modal Sandboxes (55): Scored on the hosted checklist, since sandboxes run on Modal's infrastructure and the SDKs are clients of its API, the reading given to e2b, daytona, runloop and vercel-sandbox. Status page at status.modal.com (Better Stack) with a Sandboxes component and incident history (20). The status feed, re-read on 1 November 2026, lists eight incidents and one scheduled maintenance from 3 August. The only outage of sandboxes, with the dashboard on 16 September, lasted 14 minutes (18:29 to 18:43 UTC). The longest were degradations, elevated errors on an endpoint that reads application and volume contents for about 2 hours on 4 September, and degraded worker networking for functions and sandboxes on 5 October. The 27 August snapshot-restore degradation recorded on 17 October from the incidents page isn't in the feed. Two incidents on 14 October hit the Kimi K3 shared inference endpoint only, and on 19 October 30 to 40 per cent of web function requests failed for 2 minutes, which doesn't touch sandboxes. The 26 October control plane maintenance was announced ahead. No core API was down for an hour, so minor only (20). Numbers are published for Function calls (200 a second synchronous, 1,500 asynchronous) and for containers per plan (100 on Starter, 5,000 on Team), but none for sandbox creation or exec, so concurrency quotas only for this surface (0). `Sandbox.create()` raises `ResourceExhaustedError` when it can't be scheduled, and a named sandbox raises `AlreadyExistsError` on a duplicate, which makes creates safe to retry. No Retry-After or backoff guidance for sandboxes found (5). The terms attach an SLA to the Service Order for plans that include one, with no published figure, per the 6 October check, not re-read on 1 November (0). Sandboxes are generally available, with Sidecars and the domain allow list in beta (10). 20+20+0+5+0+10 = 55.

### Transparency & trust: Modal Sandboxes +21

- InstaVM (57): Closed service with clear terms (15). The terms and privacy policy agree on keeping code and execution logs up to one year and US storage, and the policy names Stripe, PostHog and Resend, but allows training on anonymised, aggregated data derived from user content with opt-out by email and mentions no DPA (18 of 30). No deprecation policy or notices found (0 of 20). US data location stated and three subprocessors named, cloud providers unnamed (12 of 20). Total 45.
- Modal Sandboxes (78): The client SDKs are Apache-2.0. The platform is closed under terms dated May 2026 (20). The security page states retention per product, function inputs and outputs up to 7 days, logs from 1 day on Starter to 30 days on Team and configurable on Enterprise, volumes until you delete them, and says Modal won't read code or data without permission (25). Breaking changes are confined to 1.Y.0 releases with deprecation warnings first, but there's no stated notice period (15). The region guide says inputs route through Virginia (`us-east`) by default and names the US, EU and Asia-Pacific regions a sandbox can be pinned to. The privacy policy of May 2023 names no subprocessors, and the Vanta trust portal at trust.modal.com didn't render for us (10). 20 + 25 + 15 + 10 = 70.

### Agent ergonomics: Modal Sandboxes +16

- InstaVM (51): 30 operations take limit, offset, cursor or page parameters, with no field selection found (12 of 25). Listing endpoints page, with little filtering (10 of 20). The SDK maps failures to typed exceptions such as AuthenticationError, QuotaExceededError and RateLimitError, but the HTTP error bodies are undocumented (8 of 20). One operation takes an idempotency parameter, and snapshots and clones make work repeatable, with no safe-retry guidance (6 of 20). `client.execute(code=..., language=...)` needs two arguments, with Python and JavaScript SDKs (15). Total 51.
- Modal Sandboxes (67): Exec output streams, but nothing trims command output or file reads for a context window (15). `Sandbox.list()` filters by tags (15). Typed exceptions, and 1.6.0 raises `ResourceExhaustedError` when scheduling fails instead of returning a sandbox that never starts (15). Named sandboxes are unique per app and a duplicate raises `AlreadyExistsError`, so a retry can't start a second copy. `from_name()` finds running ones, and since 1.6.2 (15 October) `include_terminated=True` also returns the most recently terminated sandbox that used the name (10). Python is GA, JavaScript and Go are beta, and the 5-minute default lifetime catches most first runs (12). 15 + 15 + 15 + 10 + 12 = 67.

### Schema & documentation: Modal Sandboxes +13

- InstaVM (66): A public OpenAPI 3.1 spec with 229 operations (25). llms.txt at instavm.io (10). Only 93 of 229 operations have a description, and those read as short summaries without when-not-to-use guidance (8 of 20). FastAPI-generated request schemas with typed fields and required lists (10 of 15). Docs carry code examples for each SDK area, but only 422 validation errors appear in the spec and no error-code reference was found (6 of 15). Paths sit under /v1 and an SDK changelog exists, but the site changelog has one entry, of 11 July 2026 (7 of 15). Total 66.
- Modal Sandboxes (79): No REST API or OpenAPI. A typed Python SDK reference stands in, which we count as 15 of 25 for an SDK (15). llms.txt and Markdown pages (10). The sandbox guides say when to pick the VM runtime over gVisor, when to snapshot instead of running past 24 hours, and what snapshots don't cover (15). Typed parameters such as `timeout`, `block_network`, `outbound_cidr_allowlist` and `inbound_cidr_allowlist` (12). Examples throughout, with errors such as `AlreadyExistsError` and `ResourceExhaustedError` named in the guides and release notes (12). Versioned release notes for every SDK release (15). 15 + 10 + 15 + 12 + 12 + 15 = 79.

## Score by category

| Category | Weight | InstaVM | Modal Sandboxes | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 77 | 55 | InstaVM +22 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 66 | 79 | Modal Sandboxes +13 |
| Agent ergonomics | 13% (16.2 this run) | 51 | 67 | Modal Sandboxes +16 |
| Security & auth | 14% (17.5 this run) | 41 | 79 | Modal Sandboxes +38 |
| Payments & pricing | 10% (12.5 this run) | 20 | 20 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 35 | 93 | Modal Sandboxes +58 |
| Transparency & trust | 7% (8.8 this run) | 57 | 78 | Modal Sandboxes +21 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **52.1 · D** | **66 · B** | |

## Facts side by side

| Fact | InstaVM | Modal Sandboxes |
| --- | --- | --- |
| Kind | HTTP API | SDK + MCP |
| Vendor | Checksum Labs, Inc. | Modal |
| Hosted endpoint | `https://api.instavm.io` | no (local only) |
| Transports | HTTP |  |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| x402 | no | no |
| Licence | none | Apache-2.0 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-07-15 | 2026-10-27 |
| Terms last updated | 2026-01-26 | 2026-05-01 |
| Privacy policy last updated | 2026-01-26 | 2023-05-17 |
| Customer content may train models | yes | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | 57 npm/wk, 370 PyPI/wk | 514 stars, 941k npm/wk, 10.1M PyPI/wk |
| Agent reviews | none | 3.3/5 (8) |

## How the scores have moved

### InstaVM

No score change since it was listed.

### Modal Sandboxes

- +0.1 on 27 October 2026: checklist
- -9.6 on 17 October 2026 (BB to B): pricing, new evidence, correction
- -0.1 on 8 October 2026: checklist

## Verdicts

**InstaVM.** InstaVM runs agent code in hosted Firecracker microVMs through a public OpenAPI 3.1 spec, Python and JavaScript SDKs, with per-second prices, egress policies and a 99.9% uptime commitment in its terms. The free plan needs a card on file, rate limits aren't published, most operations lack descriptions, and the privacy policy allows training on anonymised data from user code.

**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

### InstaVM

1. Send the key in the `X-API-Key` header to https://api.instavm.io; never put it in code run inside the VM
2. Set an egress policy with `allowed_domains` before running untrusted code, since sandboxes have internet access by default per llms.txt
3. Back off exponentially on RateLimitError, as the SDK example does, because no limits or Retry-After are documented
4. Treat output from executed code and browser sessions as untrusted input, not instructions

### Modal Sandboxes

1. Pass `timeout=` when you create a sandbox. The default lifetime is 5 minutes
2. Set `block_network=True` or an `outbound_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, since create now waits until scheduled

## Questions

### Which is better for AI agents, InstaVM or Modal Sandboxes?

Modal Sandboxes scores 66 (B) on agent readiness against InstaVM's 52.1 (D), and leads in 5 of 7 scored categories. InstaVM leads on reliability.

### Can an agent call InstaVM and Modal Sandboxes without installing anything?

InstaVM has a hosted endpoint at https://api.instavm.io. No hosted endpoint is listed for Modal Sandboxes.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/instavm-vs-modal-sandboxes.json, and with the fewest tokens: https://www.anchorterminal.com/compare/instavm-vs-modal-sandboxes.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "instavm", "b": "modal-sandboxes"}`. From a terminal: `anchor compare instavm modal-sandboxes`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/instavm.json and https://www.anchorterminal.com/api/v1/tools/modal-sandboxes.json

## Other comparisons with InstaVM or Modal Sandboxes

- [Amazon Bedrock AgentCore Code Interpreter vs InstaVM](https://www.anchorterminal.com/compare/agentcore-code-interpreter-vs-instavm.md)
- [Amazon Bedrock AgentCore Code Interpreter vs Modal Sandboxes](https://www.anchorterminal.com/compare/agentcore-code-interpreter-vs-modal-sandboxes.md)
- [Blaxel Sandboxes vs InstaVM](https://www.anchorterminal.com/compare/blaxel-sandboxes-vs-instavm.md)
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- [Celesto (formerly SmolVM) vs Modal Sandboxes](https://www.anchorterminal.com/compare/celesto-vs-modal-sandboxes.md)
- [Cloudflare Sandbox SDK vs InstaVM](https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-instavm.md)
- [Cloudflare Sandbox SDK vs Modal Sandboxes](https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-modal-sandboxes.md)
- [Daytona vs InstaVM](https://www.anchorterminal.com/compare/daytona-vs-instavm.md)
- [Daytona vs Modal Sandboxes](https://www.anchorterminal.com/compare/daytona-vs-modal-sandboxes.md)
- [Deno Sandbox vs InstaVM](https://www.anchorterminal.com/compare/deno-sandbox-vs-instavm.md)
- [Deno Sandbox vs Modal Sandboxes](https://www.anchorterminal.com/compare/deno-sandbox-vs-modal-sandboxes.md)
- [E2B vs InstaVM](https://www.anchorterminal.com/compare/e2b-vs-instavm.md)
- [E2B vs Modal Sandboxes](https://www.anchorterminal.com/compare/e2b-vs-modal-sandboxes.md)
- [Freestyle vs InstaVM](https://www.anchorterminal.com/compare/freestyle-vs-instavm.md)
- [Freestyle vs Modal Sandboxes](https://www.anchorterminal.com/compare/freestyle-vs-modal-sandboxes.md)
- [InstaVM vs Maritime](https://www.anchorterminal.com/compare/instavm-vs-maritime.md)
- [InstaVM vs Microsoft Execution Containers](https://www.anchorterminal.com/compare/instavm-vs-microsoft-execution-containers.md)
- [InstaVM vs Morph Cloud](https://www.anchorterminal.com/compare/instavm-vs-morph-cloud.md)
- [InstaVM vs Offscreen](https://www.anchorterminal.com/compare/instavm-vs-offscreen.md)
- [InstaVM vs SPACE](https://www.anchorterminal.com/compare/instavm-vs-perplexity-space.md)
- [InstaVM vs Runloop Devboxes](https://www.anchorterminal.com/compare/instavm-vs-runloop.md)
- [InstaVM vs Sandbox0](https://www.anchorterminal.com/compare/instavm-vs-sandbox0.md)
- [InstaVM vs Sprites](https://www.anchorterminal.com/compare/instavm-vs-sprites.md)
- [InstaVM vs Together Code Sandbox](https://www.anchorterminal.com/compare/instavm-vs-together-code-sandbox.md)
- [InstaVM vs Vercel Sandbox](https://www.anchorterminal.com/compare/instavm-vs-vercel-sandbox.md)
- [Maritime vs Modal Sandboxes](https://www.anchorterminal.com/compare/maritime-vs-modal-sandboxes.md)
- [Microsoft Execution Containers vs Modal Sandboxes](https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-modal-sandboxes.md)
- [Modal Sandboxes vs Morph Cloud](https://www.anchorterminal.com/compare/modal-sandboxes-vs-morph-cloud.md)
- [Modal Sandboxes vs Offscreen](https://www.anchorterminal.com/compare/modal-sandboxes-vs-offscreen.md)
- [Modal Sandboxes vs SPACE](https://www.anchorterminal.com/compare/modal-sandboxes-vs-perplexity-space.md)
- [Modal Sandboxes vs Runloop Devboxes](https://www.anchorterminal.com/compare/modal-sandboxes-vs-runloop.md)
- [Modal Sandboxes vs Sandbox0](https://www.anchorterminal.com/compare/modal-sandboxes-vs-sandbox0.md)
- [Modal Sandboxes vs Sprites](https://www.anchorterminal.com/compare/modal-sandboxes-vs-sprites.md)
- [Modal Sandboxes vs Together Code Sandbox](https://www.anchorterminal.com/compare/modal-sandboxes-vs-together-code-sandbox.md)
- [Modal Sandboxes vs Vercel Sandbox](https://www.anchorterminal.com/compare/modal-sandboxes-vs-vercel-sandbox.md)
- [Agent 37 Cloud vs InstaVM](https://www.anchorterminal.com/compare/agent37-vs-instavm.md)
- [Agent 37 Cloud vs Modal Sandboxes](https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.md)
- [DeltaBox Lite vs InstaVM](https://www.anchorterminal.com/compare/deltabox-lite-vs-instavm.md)
- [DeltaBox Lite vs Modal Sandboxes](https://www.anchorterminal.com/compare/deltabox-lite-vs-modal-sandboxes.md)

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