Vercel Sandbox vs Cloudflare Sandbox SDK
Answer in brief
Choose Vercel Sandbox for teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering; choose Cloudflare Sandbox SDK for teams building on Cloudflare Workers that want per-user sandboxes with egress and credentials controlled in code. Vercel Sandbox uses Firecracker microVM isolation; Cloudflare Sandbox SDK uses MicroVM (Containers) isolation and is open source.
Vercel Sandbox vs Cloudflare Sandbox SDK at a glance
| Attribute | Vercel Sandbox | Cloudflare Sandbox SDK |
|---|---|---|
| What it is | Firecracker microVM sandboxes on Vercel’s infrastructure, persistent by default and billed on active CPU, with fine-grained egress control. | A TypeScript SDK for Cloudflare Workers that runs untrusted code in Linux sandboxes backed by Cloudflare Containers and Durable Objects. |
| Isolation | Firecracker microVM with a dedicated kernel per sandbox | Each container instance is a microVM with its own kernel and network (per Cloudflare docs); Dynamic Workers (V8 isolates) available for JavaScript-only code |
| Open source | No (SDK and CLI Apache-2.0) | Yes (SDK Apache-2.0 (runs only on Cloudflare)) |
| Self-host / BYOC | No / No | No / No |
| SDKs | JavaScript/TypeScript, Python | TypeScript (Workers) |
| Cold start (vendor claim) | “Start in milliseconds” (vendor claim, no figure); snapshot resume faster than fresh start | Container cold starts “often in the 1–3 second range” depending on image (vendor docs) |
| Max session | 5 min default; up to 45 min per session on Hobby and 24 hours on Pro/Enterprise; persistent sandboxes can be resumed indefinitely | No fixed cap; runs while its Durable Object is active, then up to a 6-hour inactivity timeout |
| Persistence | Persistent by default — filesystem auto-snapshotted on stop and restored on resume; manual snapshots; Drives (beta) and S3 mounts | Ephemeral disk by default; container snapshots (up to 20 GB, 30 days), directory backups to R2, S3/R2 bucket mounts and Durable Object storage |
| GPU | Not documented | Not documented |
| Networking | Firewall modes allow-all, deny-all or domain/CIDR rules, updatable at runtime; credential brokering injects headers so secrets never enter the sandbox; public URLs for up to 15 ports | Egress controlled from Worker code: disable internet and intercept outbound HTTP to allow specific hosts and inject credentials; preview URLs routed through your Worker |
| Pricing | Active CPU $0.128/hour (billed only while CPU is used) + provisioned memory $0.0212/GB-hour + $0.60 per million creations, plus storage and transfer (iad1 rates) | Cloudflare Containers rates in 10 ms increments: $0.000020 per vCPU-second (active) + $0.0000025 per GiB-second + disk; requires the $5/month Workers Paid plan |
| Compliance | Runs on Vercel infrastructure with SOC 2 Type II (company-wide) | Not documented |
| Best for | Teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering | Teams building on Cloudflare Workers that want per-user sandboxes with egress and credentials controlled in code |
Verified November 8, 2026 from each provider’s documentation. Cold-start figures are vendor claims, not our measurements.
Which should you choose?
Choose Vercel Sandbox if…
- You deploy on Vercel or use the AI SDK
- You want secrets brokered outside the sandbox
- Your agents idle while waiting on models and you want active-CPU billing
- You want persistent-by-default microVMs
Choose Cloudflare Sandbox SDK if…
- You build on Cloudflare Workers and Durable Objects
- You want egress and credentials controlled in your own code
- You want global placement on Cloudflare’s network
- You want a lighter isolate option for JS-only code
Both are worth piloting with your own image and region. See the full Vercel Sandbox profile and Cloudflare Sandbox SDK profile, or the complete comparison.
Frequently asked questions
Is Vercel Sandbox or Cloudflare Sandbox SDK better for AI agents?
Neither is better for every workload. Vercel Sandbox is best for teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering. Cloudflare Sandbox SDK is best for teams building on Cloudflare Workers that want per-user sandboxes with egress and credentials controlled in code.
Which is open source, Vercel Sandbox or Cloudflare Sandbox SDK?
Cloudflare Sandbox SDK is open source (SDK Apache-2.0 (runs only on Cloudflare)); Vercel Sandbox is not.
How do Vercel Sandbox and Cloudflare Sandbox SDK isolate code?
Vercel Sandbox: Firecracker microVM with a dedicated kernel per sandbox. Cloudflare Sandbox SDK: Each container instance is a microVM with its own kernel and network (per Cloudflare docs); Dynamic Workers (V8 isolates) available for JavaScript-only code.
Sources
Cite this page
Agent Sandboxes. (2026). Vercel Sandbox vs Cloudflare Sandbox SDK. agentsandboxes.org. Last reviewed November 8, 2026. https://agentsandboxes.org/compare/vercel-sandbox-vs-cloudflare-sandbox/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.