# Fly Sprites vs CodeSandbox: pricing, persistence and limits Runtime Cloud (withruntime.com) is 73% cheaper than either. CodeSandbox bills a fixed size by the minute. ## Which is better, Fly Sprites or CodeSandbox? It depends on how busy and how large the machine is. For agents that mostly wait on a model, Runtime has the lowest bill: $0.64 for 1,000 one-minute runs, against $2.40 on Sprites and $2.48 on CodeSandbox. Runtime meters CPU at a lower rate, because it bills per second. Pick Fly Sprites for a 100 GB disk that costs little while asleep and takes filesystem checkpoints in about a second. Pick CodeSandbox for large fixed VMs, up to 64 cores and 128 GB, or for 250 VMs running concurrently on its Scale plan. ## At a glance CodeSandbox's figures come from Together's documentation of the CodeSandbox SDK. CodeSandbox is a Together company. | | Fly Sprites | CodeSandbox SDK | Runtime | | ------------ | ------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------- | -------------------------------------------------------------- | | Isolation | Firecracker microVM | Firecracker microVM | Firecracker microVM, own kernel | | CPU | $0.0385 per CPU-hour of measured CPU | Inside a fixed VM size | $0.025 per vCPU-hour of measured CPU, with a small floor | | Memory | $0.021875 per GB-hour of memory in use, managed by Fly | Set by the size: Nano has 2 cores and 4 GB, $0.1486 an hour | $0.0075 per reserved GiB-hour | | Billing unit | Usage while awake | By the minute, rounded up | By the second | | Disk | 100 GB, billed on what you use | Inside the VM | Included while running | | Plan fee | None required; optional monthly plans | Build plan free with 10 VMs concurrently; Scale $170 per month for 250 | None; prepaid credit from $10 | | Free start | $30 of trial credit | The free Build plan | 100 free hours of a 1 GB machine in the first 30 days, no card | | State | Disk kept; memory kept in a warm pause, dropped when cold | Memory snapshot and restore at any point | Pause, snapshot and fork keep files, memory and processes | ## Is paying for what you use cheaper than a fixed size? Not at every load. Sprites meter both CPU and memory, but the memory meter is $0.021875 per GB-hour. A Sprite holding 4 GB pays $2.19 per 1,000 runs for its memory alone, close to the $2.48 a CodeSandbox Nano VM, with 2 cores and 4 GB, pays for everything. With both CPUs busy, the Sprite costs more: $3.47 on Sprites against the same $2.48 on CodeSandbox, whose price does not change with the work. The gap opens when a Sprite uses little memory. At 1 GB in use, the same 1,000 runs cost $0.76 on Sprites, against $1.24 on a CodeSandbox Pico VM (2 cores, 1 GB, 5 credits an hour). Runtime, with 1 GiB reserved, costs $0.26 for the same runs. So the answer depends on the price of each meter, not only on whether the provider meters usage. Runtime measures CPU at $0.025 a vCPU-hour and reserves memory at $0.0075 per GiB-hour, below both other providers at every size in this page. ## Cost for the same job 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 mostly waits for a model. The Sprite is assumed to use all 4 GB for the whole minute. The CodeSandbox VM is a Nano, which costs 10 credits an hour at $0.01486 per credit. ``` Sprites CPU 1,000 × 20 s / 3,600 × $0.0385 = $0.21 Memory 1,000 × 90 s / 3,600 × 4 × $0.021875 = $2.19 Total $2.40 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 per month, that is $240.14 on Sprites, $247.67 on CodeSandbox and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $3.47 on Sprites and $2.48 on CodeSandbox, so Runtime is cheaper however busy the sandbox is. The Sprite figure includes the 30 seconds or so that a Sprite stays awake and billed after its run. Plan fees, storage, network and free credits are left out. ## Which one to pick - **Pick Fly Sprites** for a long-lived computer an agent returns to, with a 100 GB disk that costs little while it sleeps and filesystem checkpoints that take about a second. - **Pick CodeSandbox** for large fixed VMs, up to 64 cores and 128 GB, or for 250 VMs running concurrently on its Scale plan. - **Pick Runtime** for the lowest price of the three at this size, busy or waiting, memory sized to the job, per-second billing, and pause that keeps memory while you have credit. ## Runtime Cloud Runtime runs the same job for 73% less than Sprites and 74% less than CodeSandbox. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $2.40 on Fly Sprites, $2.48 on CodeSandbox and $0.64 on Runtime. Runtime meters CPU like Sprites, at 35% below the rate, and bills per second where CodeSandbox rounds up to the minute. Rates checked 25 October 2026. Every sandbox is a Firecracker microVM, and a pause keeps its memory. Start on the free usage with `npx withruntime login`. See the [migration guide](/docs/migrate) to move existing code. ## Switch from either one From Sprites, `client.createSprite(name)` becomes `Sandbox.create()` and `sprite.execFile(cmd, args)` becomes `exec([cmd, ...args])`. From CodeSandbox, create a sandbox where you would start a VM, and set its memory directly instead of picking a size tier: ```ts import { Runtime } from "withruntime"; const runtime = new Runtime(); const sbx = await runtime.sandboxes.create({ vcpu: 2, memoryMiB: 1024 }); try { await sbx.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n"); const run = await sbx.exec(["python3", "/workspace/invoice.py"]); console.log(run.stdout); } finally { await sbx.stop(); } ``` Or give your coding agent the one instruction in [migration](/docs/migrate). It switches the project on a branch, tests it on the free usage, and reports the monthly saving. `npx withruntime compare --from fly` (or `--from codesandbox`) prices what you ran at the old provider's rates. Credit you add within 30 days of signing up is matched, up to $1,000 in total. The full comparisons are [Runtime vs Fly.io](/docs/fly-alternative) and [Runtime vs CodeSandbox](/docs/codesandbox-alternative). The [sandbox cost calculator](/calculators/sandbox-cost-calculator) prices other sizes. ## Sources Rates checked 25 October 2026; the Sprites, Sprites lifecycle and Together pages read 26 October 2026. - [Fly.io pricing](https://fly.io/pricing/), [Sprites](https://fly.io/sprites/), [Sprites lifecycle](https://docs.fly.io/sprites/concepts/lifecycle/) - [Together: CodeSandbox SDK](https://docs.together.ai/docs/together-code-sandbox-legacy), [CodeSandbox SDK pricing](https://codesandbox.io/docs/sdk/pricing) - Runtime [pricing](/docs/pricing) Facts on this page were checked on 26 October 2026.