Fly Machines vs Runloop: pricing, devboxes and limits

Which is better, Fly Machines or Runloop?

It depends on whether you need a sandbox or a platform built around one. For agents that mostly wait on a model, Runtime has the lowest bill: $0.64 for 1,000 one-minute runs, against $1.53 on Fly Machines and $5.33 on Runloop. Its pause keeps processes running. Pick Fly Machines for a service that stays up near its users, in any of 17 regions. Pick Runloop if you want evaluation tooling, a deployment in your own cloud, or a stated compliance posture.

At a glance

	Fly Machines	Runloop	Runtime
Isolation	Firecracker microVM	microVM, with a container inside	Firecracker microVM, own kernel
CPU	Inside a fixed size, billed while started	$0.108 per CPU-hour while the devbox runs	$0.025 per vCPU-hour of measured CPU, with a small floor
Memory	Inside the size; more at $6 per GB per month	$0.0252 per GB-hour	$0.0075 per reserved GiB-hour
Disk	Root disk temporary; Fly Volumes for files that last	$0.00034236 per GB-hour; `MEDIUM` comes with 8 GB	Included while running
2 vCPU, 4 GB	`performance-2x`, $0.0916704 an hour (`iad`)	`MEDIUM`, $0.3195 an hour	$0.08 an hour fully busy, $0.03125 waiting
Sizes	Fixed sizes up to 16 performance vCPUs and 128 GB	`X_SMALL` to `XX_LARGE`, or custom up to 16 CPUs, 64 GiB	Up to 16 vCPUs and 64 GiB paid, chosen apart
Plan fee	None; pay as you go	Basic free; Pro $250 per month plus usage	None; prepaid credit from $10
Free start	Not stated on the pricing page	$50 of credit, no card	100 free hours of a 1 GB machine in the first 30 days, no card
Suspend, resume	Keeps memory only for Machines with 2 GB or less	Keeps the disk; processes restart	Pause keeps files, memory and processes while you have credit

Why does a Runloop devbox cost almost four times a Machine?

The rates. Runloop bills $0.108 per CPU-hour and $0.0252 per GB-hour of memory. It bills its disk by the GB-hour. Its MEDIUM devbox, with 2 CPUs, 4 GB and 8 GB of disk, comes to $0.3195 an hour. A Fly performance-2x with 4 GB is $0.0916704, about 29% of that. Both bill the whole size for as long as it runs, busy or waiting.

The premium pays for what surrounds the VM rather than the VM itself. Runloop evaluates models on your own workload, generates RL rollouts, deploys into your own cloud account, and states SOC 2, HIPAA and GDPR readiness. A Fly Machine is a general-purpose VM in 17 regions, with volumes and Managed Postgres in the same account.

Runtime is priced below both for agent work, since it bills measured CPU at $0.025 a vCPU-hour. Agent evals and SWE-bench shows how to run a benchmark harness on it.

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 Fly Machine is a performance-2x with 4 GB. The Runloop devbox is a MEDIUM.

Machines$1.53

Size: 1,000 × 60 s / 3,600 × $0.0916704; $1.53

Runloop$5.33

CPU: 1,000 × 60 s / 3,600 × 2 × $0.108; $3.60
Memory: 1,000 × 60 s / 3,600 × 4 × $0.0252; $1.68
Disk: 1,000 × 60 s / 3,600 × 8 × $0.00034236; $0.05

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

At 100,000 runs per month, the cost is $152.78 on Fly Machines, $532.56 on Runloop and $63.89 on Runtime. With both CPUs busy for the whole minute, the job costs $1.33 on Runtime, against $1.53 on Machines and $5.33 on Runloop. Runtime is cheaper however busy the sandbox is. Plan fees, storage while suspended, network and free credits are left out.

What survives a suspend?

On Runloop, only the disk survives. Its lifecycle docs say in-memory state is not kept across suspend and resume. The devbox keeps its ID and SSH keys, and a suspended devbox is charged for storage until it is shut down. Compute stops while it is suspended.

A Fly Machine's suspend keeps the whole VM, memory and open files included, and resumes in a few hundred milliseconds. It needs 2 GB of memory or less, though, so the 4 GB size here can only be stopped. Fly also says a deploy, a host migration or maintenance discards a suspended snapshot.

A paused Runtime sandbox keeps its files, memory and running processes at any size, while you have credit, at $0.08 per GB per month. A request to it wakes it by itself.

Which one to pick

Pick Fly Machines for a service that stays up near its users, in any of 17 regions.
Pick Runloop if you want evaluation tooling, a deployment in your own cloud, or a stated compliance posture.
Pick Runtime for agent sandboxes that pause and resume with their processes still running, measured CPU, and no plan fee.

Runtime Cloud

Runtime runs the same job for 58% less than a Fly Machine and 88% less than Runloop. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $1.53 on Fly Machines, $5.33 on Runloop and $0.64 on Runtime, because Runtime bills the CPU your code uses rather than the CPUs it holds. A paused Runtime sandbox keeps its memory and running processes, which neither rival's suspend does at this size. Rates checked 25 October 2026.

There is no plan fee. You can start on the free usage with npx withruntime login. The migration guide shows how to move existing code.

Switch from either one

A suspended devbox that must restart its processes becomes a paused sandbox that carries on where it stopped:

TypeScriptimport { Sandbox } from "withruntime";const sbx = await Sandbox.create({ timeoutSeconds: 600 });await sbx.exec("echo state > /workspace/state.txt");await sbx.pause(); // memory, files and processes kept; compute billing stopsconst again = await Sandbox.connect(sbx.id);await again.wake({ timeoutSeconds: 1200 });console.log((await again.exec("cat /workspace/state.txt")).stdout);await again.stop();

Or give your coding agent the one instruction in migration. It switches the project on a branch, tests it on the free usage, and reports the monthly saving. npx withruntime compare --from fly-machines (or --from runloop) 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 side-by-sides are Runtime vs Fly.io and Runtime vs Runloop.

Sources

Fly.io prices checked 25 October 2026.

Rates checked 25 October 2026. The Fly suspend page and Runloop's sizes and lifecycle pages were read 26 October 2026.

Fly.io pricing, Machine suspend and resume, Fly.io regions
Runloop pricing, Devbox sizes, Devbox lifecycle, Runloop
Runtime pricing and JavaScript SDK

Facts on this page were checked on 26 October 2026.

Fly Machines vs Runloop pricing, devboxes and limits