Vercel Sandbox vs Fly Sprites: pricing, memory and idle time

Both bill measured CPU in Firecracker microVMs. Vercel bills provisioned memory; Sprites bill memory in use and pause themselves when idle.

Runtime runs the same job for 70% less than Vercel and 81% less than Sprites. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $2.12 on Vercel, $3.31 on Sprites and $0.64 on Runtime. All three bill CPU as it is used; Runtime's memory rate, $0.0075 per GiB-hour, is about a third of Vercel's and a sixth of Sprites'. Rates checked 23 September 2026.

At a glance

Vercel's figures are at the rates of its default iad1 region.

	Vercel Sandbox	Fly Sprites	Runtime
Isolation	Firecracker microVM, own kernel	Firecracker microVM	Firecracker microVM, own kernel
CPU	$0.128 per active CPU-hour	$0.07 per CPU-hour of measured CPU	$0.025 per vCPU-hour of measured CPU, with a small floor
Memory	$0.0212 per provisioned GB-hour; 2 GB per vCPU	$0.04375 per GB-hour of memory in use	$0.0075 per reserved GiB-hour
Size	Up to 8 vCPUs and 16 GB on Pro	Memory managed by Fly, 100 GB disk	vCPUs and memory chosen per sandbox
Plan fee	Hobby allowance free; usage beyond it needs Pro	None required; optional monthly plans	None; prepaid credit from $10
Free start	5 active CPU-hours and 420 GB-hours a month on Hobby	$30 of trial credit	50 sandbox hours, no card
When idle	Runs until its timeout or stop(); stop keeps the filesystem	Pauses itself; memory kept at first, the disk kept always	Pauses after the idle time you set, memory and processes kept
Stored state	Snapshots $0.08 per GB-month, expire 30 days after last use by default	Sleeping disk $0.02 per GB-month	Paused storage $0.08 per GB-month, kept 1 to 365 days
Interfaces	JavaScript and Python SDKs	API, CLI, MCP server; JavaScript, Python, Go, Elixir SDKs	API, CLI, MCP server, JavaScript and Python SDKs

Which is cheaper, Vercel Sandbox or Sprites?

Vercel, for an agent that mostly waits, because memory is most of the bill. Sprites charge $0.04375 per GB-hour of memory in use, about twice Vercel's $0.0212 per provisioned GB-hour, so a waiting 4 GB sandbox costs about $0.175 an hour on Sprites and $0.085 on Vercel. Sprites' CPU is cheaper, $0.07 an hour against $0.128, so the gap closes as the code gets busier. The order flips when a one-minute run uses about 93 CPU-seconds of its 120.

Two things move the Sprite figure down. It bills the memory it actually uses, so a job that uses 1 GB for the minute pays $1.12 for these runs instead of $3.31. And it pauses by itself, so a Sprite you forget costs little. It also stays awake for about 30 seconds after its last activity unless you delete it.

What happens between tasks?

This decides the cost of an agent that works in bursts. A Sprite pauses itself when idle and keeps its disk; its memory is kept at first, then dropped when it goes cold, at a time you do not choose. A Vercel sandbox runs until its timeout or a stop(), which keeps its filesystem; processes start again next session.

A Runtime sandbox pauses after the idle time you set, keeps its memory and running processes for the retention you choose, and wakes on the next request:

Pythonfrom withruntime import Sandboxdev = Sandbox.get_or_create("agent-dev", idle_pause_seconds=300)dev.exec("git --version", check=True)# Five quiet minutes later it pauses; the next call wakes it where it stopped.print(Sandbox.get_or_create("agent-dev").exec("uptime").stdout)

See how to pause and resume a sandbox.

Cost for the same job

1,000 runs of a 2 vCPU sandbox with 4 GiB, or 4 GB on Vercel. The Sprite is assumed to use all 4 GB for the whole minute. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model.

TextVercel   CPU    1,000 × 20 s / 3,600 × $0.128       = $0.71         Memory 1,000 × 60 s / 3,600 × 4 × $0.0212  = $1.41         Total                                         $2.12Sprites  CPU    1,000 × 20 s / 3,600 × $0.07        = $0.39         Memory 1,000 × 60 s / 3,600 × 4 × $0.04375 = $2.92         Total                                         $3.31Runtime  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 that is $212.44 on Vercel, $330.56 on Sprites and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $5.68 on Vercel and $5.25 on Sprites, so Runtime is cheaper however busy the sandbox is. Plan fees, creations, storage, network and free allowances are left out.

Which one to pick

• Pick Vercel Sandbox if your app is on Vercel, or you need sandboxes in a region you choose, from 19, with up to 10,000 at once on Pro.
• Pick Sprites for long-lived agent computers that sleep cheaply: a sleeping Sprite's disk costs $0.02 per GB-month, with SDKs for Go and Elixir as well as JavaScript and Python.
• Pick Runtime for measured CPU at about a fifth of Vercel's rate and a third of Sprites', memory sized to the job, and a pause that keeps memory for as long as you choose.

Switch from either one

From Vercel Sandbox, change the import and keep the code, with no Vercel project or token:

TypeScriptimport { Sandbox } from "withruntime/vercel"; // was: from "@vercel/sandbox"

From Sprites, client.createSprite(name) becomes Sandbox.getOrCreate(name) (or Sandbox.create() for a one-off), sprite.execFile(cmd, args) becomes exec([cmd, ...args]), and sprite.delete() becomes stop():

TypeScriptimport { 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();}

Or give your coding agent the one instruction in migration: it switches the project on a branch, tests it on the free trial and reports the monthly saving. npx withruntime switch --from vercel (or --from fly) before your first top-up matches that top-up with credit, up to $100. The full side-by-sides are Runtime vs Vercel Sandbox and Runtime vs Fly.io.

Sources

Vercel Sandbox pricing rechecked 25 September 2026; the rest checked 23 September 2026.

• Vercel Sandbox pricing, Understanding Vercel Sandboxes
• Fly.io pricing, Sprites, Sprites documentation, Sprites lifecycle and persistence
• Runtime pricing

Facts on this page were checked on 25 September 2026.