# Cloudflare Sandbox vs CodeSandbox SDK: pricing, isolation and limits Cloudflare bills active CPU in 10 ms steps; CodeSandbox bills a fixed VM size by the minute, rounded up, busy or not. **Runtime charges 53% less than Cloudflare and 74% less than CodeSandbox for the same agent job.** A thousand one-minute runs at 2 vCPU come to $1.35 on Cloudflare, $2.48 on CodeSandbox and $0.64 on Runtime. Runtime counts measured CPU second by second, never rounds a run up to a whole minute, and takes any mix of vCPUs and memory you ask for. Rates checked 23 September 2026. ## At a glance The Sandbox SDK is billed as Cloudflare Containers, whose rates appear here. CodeSandbox's rates are from Together's documentation of the CodeSandbox SDK; CodeSandbox is a Together company. | | Cloudflare Sandbox SDK | CodeSandbox SDK | Runtime | | ---------------- | -------------------------------------------------------- | --------------------------------------------------- | -------------------------------------------------------- | | Isolation | A container in its own VM | Firecracker microVM | Firecracker microVM, own kernel | | CPU | $0.072 per active vCPU-hour | By VM size: Nano (2 cores, 4 GB) is $0.1486 an hour | $0.025 per vCPU-hour of measured CPU, with a small floor | | Memory | $0.009 per provisioned GiB-hour; at least 3 GiB per vCPU | Inside the VM size | $0.0075 per reserved GiB-hour | | Billing step | 10 ms of CPU | A minute, rounded up | By the second | | Largest | 4 vCPUs, 12 GiB and 20 GB of disk | 64 cores and 128 GB | vCPUs and memory chosen per sandbox | | At once | 1,500 vCPUs and 6 TiB of memory per account | 10 VMs on Build; 250 on Scale | 100 sandboxes to start on a paid account | | Plan fee | Workers Paid, at least $5 a month | Build free; Scale $170 a month | None; prepaid credit from $10 | | Snapshots, forks | A directory backed up to R2 | Memory snapshot and restore | Files, memory and running processes | ## Which is cheaper for short runs? Cloudflare, by a wide margin, and the shorter the run the wider it gets. CodeSandbox bills a Nano VM at 10 credits an hour, $0.1486, and rounds each VM's time up to the next minute, so a 40-second run is billed as 60. Cloudflare meters CPU in 10 ms steps and prices memory and disk per second. Shorten the example below to 40-second runs with the same 20 CPU-seconds of work, and 1,000 of them cost $1.03 on Cloudflare, still $2.48 on CodeSandbox, and $0.47 on Runtime. The order only changes for busy work: with a fixed price per minute, CodeSandbox becomes the cheaper rival once a one-minute run uses more than about 76 of its 120 CPU-seconds. ## Cost for the same job For the full one-minute case: 1,000 runs on 2 vCPU, 60 seconds each, 20 CPU-seconds of computing per run. CodeSandbox runs a Nano VM, which has 4 GB, and Runtime gets 4 GiB. Cloudflare's floor of 3 GiB per vCPU makes its smallest 2 vCPU shape 6 GiB, and the disk is 12 GB as in Cloudflare's example. ``` Cloudflare CPU 1,000 × 20 s × $0.000020 = $0.40 Memory 1,000 × 60 s × 6 × $0.0000025 = $0.90 Disk 1,000 × 60 s × 12 × $0.00000007 = $0.05 Total $1.35 CodeSandbox Size 1,000 × 60 s / 3,600 × $0.1486 = $2.48 Runtime CPU 1,000 × 20 s / 3,600 × $0.025 = $0.14 Memory 1,000 × 60 s / 3,600 × 4 × $0.0075 = $0.50 Total $0.64 ``` At 100,000 runs a month: $135.04 on Cloudflare, $247.67 on CodeSandbox and $63.89 on Runtime. Keep both CPUs busy for the whole minute and it is $1.33 on Runtime, $3.35 on Cloudflare and $2.48 on CodeSandbox. The Nano's price does not move at all. Cloudflare's figure assumes each sandbox is destroyed after its run; plan fees, Workers requests, Durable Object time, storage, network and free allowances are excluded. ## Is a microVM safer than Cloudflare's container? Both put a virtual machine boundary around your code. Cloudflare runs each sandbox as a container inside its own VM. CodeSandbox and Runtime run each sandbox as a Firecracker microVM with its own Linux kernel. [MicroVM vs container](/compare/microvm-vs-container) explains the difference, and [Firecracker](/glossary/firecracker) what the microVM is. On Runtime, root inside the sandbox cannot change its network, CPU, memory or cost, and a sandbox can run with its internet off or with an allow list. See [how to turn off sandbox internet](/how-to/turn-off-sandbox-internet). ## Which one to pick - **Short, bursty runs inside a Workers app:** Cloudflare Sandbox, which also places sandboxes near users on its network. - **Big machines or a large busy fleet:** the CodeSandbox SDK, with VMs up to 64 cores and 128 GB, memory snapshots, and up to 250 VMs on the Scale plan. - **Per-second billing for an agent that waits:** Runtime, whose measured CPU costs about a third of Cloudflare's rate, with any shape of vCPUs and memory and forks that copy a running sandbox, memory included. ## Moving the code Cloudflare's calls have direct equivalents, `getSandbox(env.Sandbox, name)` as `Sandbox.getOrCreate(name)`, `sandbox.exec(cmd)` as `exec` and `proxyToSandbox` as `box.previews.create(port)`, and once ported the code no longer has to live in a Worker. With CodeSandbox, start a Runtime sandbox where you started a VM, send commands through `exec`, and call `stop()` where the VM was shut down. ```ts import { Sandbox } from "withruntime"; const box = await Sandbox.create({ funding: "trial" }); try { console.log((await box.exec("python3 -c 'print(6 * 7)'", { check: true })).stdout); } finally { await box.stop(); } ``` A coding agent given the instruction in [migration](/docs/migrate) will do the port on a branch and test it on the free trial. Cloudflare users who run `npx withruntime switch --from cloudflare` before the first top-up get it matched in credit, up to $100. Full comparisons: [Runtime vs Cloudflare](/docs/cloudflare-sandbox-alternative), [Runtime vs CodeSandbox](/docs/codesandbox-alternative). ## Sources Rates checked 23 September 2026; Cloudflare's sandbox lifecycle page read 25 September 2026. - [Cloudflare Containers pricing](https://developers.cloudflare.com/containers/pricing/), [Containers limits and instance types](https://developers.cloudflare.com/containers/platform/limits/), [Containers architecture](https://developers.cloudflare.com/containers/concepts/architecture/) - [Together Code Sandbox](https://docs.together.ai/docs/together-code-sandbox), [CodeSandbox SDK pricing](https://codesandbox.io/docs/sdk/pricing) - Runtime [pricing](/docs/pricing), [security](/docs/security) Facts on this page were checked on 25 September 2026.