Runtime vs CodeSandbox

• You pay for the CPU you use. CodeSandbox bills a VM's size in credits for as long as it runs. Runtime measures the CPU your code actually uses, so time spent waiting on a model costs only a small floor, a twentieth of a vCPU.
• Idle time bills only storage. A Runtime sandbox pauses itself after 300 seconds with no activity, keeps its memory and processes, and runs its next command when a request wakes it. While paused, it pays $0.08 per GB (10⁹ bytes) of saved state a month.
• A written uptime promise. 99% API uptime a month for paid accounts, measured from outside, and 10% of a short month's charges back as credit automatically (Uptime Promise).
• Cheaper even when busy. With both CPUs working the whole time, the example job costs $1.33 on Runtime and $2.48 on CodeSandbox.
• Billed by the second. CodeSandbox rounds each VM's runtime up to the next minute. Runtime compute has no one-minute minimum.
• Any shape. CodeSandbox sells fixed VM sizes. On Runtime you choose vCPUs and memory for each sandbox and pay for no more.
• No plan fee for concurrency. More than 10 VMs at the same time on CodeSandbox needs the $170-a-month Scale plan. Runtime has no plan: a paid account runs 100 sandboxes at the same time, and support raises the limit on request.
• Secrets stay outside the sandbox. Code inside sees a placeholder; the real key is added at the egress proxy, only on HTTPS to the hosts you allow (security).
• Your agent sets itself up. It runs npx withruntime sandboxes run -- ..., shows you a link, and starts once you approve in the browser. No API key goes into a prompt or a config file, and the MCP server reuses the same connection.

Also included: a code interpreter, network allow and deny lists, custom images, volumes backed up daily, snapshots and forks with memory, private previews, a Linux desktop, metrics, webhooks, OpenTelemetry export, S3, R2 and GCS bucket mounts, identity tokens for AWS and Google Cloud and free single sign-on. Paid accounts add custom domains, TCP ports, dedicated outbound addresses and WireGuard private networks. See products.

CodeSandbox's figures come from the Together Code Sandbox documentation, which covers the CodeSandbox SDK, checked 25 October 2026.

	Runtime	CodeSandbox SDK
Isolation	Firecracker microVM, own kernel	Firecracker microVM
CPU billing	$0.025 per vCPU-hour of measured CPU, with a small floor	By VM size: Nano (2 cores, 4 GB) is $0.1486 an hour
Memory billing	$0.0075 per reserved GiB-hour	Inside the VM size
Billing unit	By the second	By the minute, rounded up
Plan fee	None; prepaid credit from $10	Build free with 10 VMs at the same time; Scale $170 a month
Free start	100 free hours of a 1 GB machine in the first 30 days, no card	The free Build plan
Snapshots, forks	Files, memory and running processes	Memory snapshot and restore

Take 1,000 runs of a 2 vCPU, 4 GiB sandbox. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that spends most of its time waiting for a model. On CodeSandbox that is a Nano VM, 10 credits an hour at $0.01486 a credit.

Runtime$0.64

CPU

1,000 × 20 s / 3,600 × $0.025

$0.14

Memory

1,000 × 60 s / 3,600 × 4 × $0.0075

$0.50

CodeSandbox$2.48

Size

1,000 × 60 s / 3,600 × $0.1486

$2.48

• Saving 74%, or $1.84 per 1,000 runs.
• Per month at 100,000 runs, $63.89 on Runtime against $247.67 on CodeSandbox.
• Busier work with both CPUs busy for the whole minute, $1.33 on Runtime against $2.48 on CodeSandbox.

Each run here is a whole minute, so CodeSandbox's rounding adds nothing; a 40-second run would still be billed as a minute there. Plan fees, storage, network and taxes are left out of both. On Runtime, inbound traffic is free, and each account's first 100 GiB out a month is free, then $0.02 per GB (10⁹ bytes). See pricing for Runtime's terms.

Give your coding agent the one instruction in migration. It replaces the CodeSandbox calls on a branch, tests them on the free usage, and tells you what you save each month. Your old code stays on the main branch until you merge.

Runtime:

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create();try {  await box.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n");  console.log((await box.exec("python3 /workspace/invoice.py", { check: true })).stdout);} finally {  await box.stop();}

• Very large machines. CodeSandbox VMs go up to 64 cores and 128 GB.
• Many VMs on a plan. The Scale plan runs 250 VMs at the same time.

Checked 23 September 2026. The rates are from Together's documentation of the CodeSandbox SDK; CodeSandbox is a Together company.

• Together: CodeSandbox SDK
• CodeSandbox SDK pricing
• Runtime pricing, security and products