Runtime

Fly Machines vs Morph: pricing, snapshots and limits

A Fly Machine bills a fixed size while started; Morph bills MCUs for a VM's size and can branch a running VM to many copies.

Runtime runs the same job for 55% less than a Fly Machine and 62% less than Morph. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $1.44 on Fly Machines, $1.67 on Morph and $0.64 on Runtime, because Runtime bills the CPU your code uses rather than the size it holds. Like Morph, it copies a running sandbox with its memory. Rates checked 23 September 2026.

Estimated compute cost

55% less than Fly Machines62% less than Morph

2 vCPUs · 4 GiB · 60 s a run · 20 CPU-seconds busy

1,000

Compute only, at list rates checked 23 September 2026 (Fly.io pricing, Morph Cloud pricing). Plan fees, network, taxes and free credits are left out. The worked example below shows the arithmetic.

At a glance

Fly Machines Morph Runtime
Isolation Firecracker microVM Full virtual machines Firecracker microVM, own kernel
How it bills A fixed size per second while started $0.05 per MCU-hour for the machine's size $0.025 per vCPU-hour of measured CPU, with a small floor
Memory Inside the size; more at $5 per GB a month Inside the MCU: 4 GB per MCU $0.0075 per reserved GiB-hour
2 vCPU, 4 GB performance-2x, $0.0861 an hour (iad) 2 MCUs, $0.10 an hour $0.08 an hour fully busy, $0.03125 waiting
Plan fee None; pay as you go Free with no credit; Developer $40 and Team $250 a month None; prepaid credit from $10
At once Not stated on the pricing page 8 devboxes free, 32 on Developer, 128 on Team 100 sandboxes on a paid account to start
Keep a running VM Suspend, for Machines with 2 GB of memory or less Snapshots of memory and disk; branches to many replicas Pause, snapshot and fork keep memory and processes

Can you snapshot and branch a running machine?

On Morph, yes, and it is the product's centre. A snapshot captures a VM's memory and disk, and Morph's Infinibranch starts hundreds of parallel replicas from one running machine. Snapshot storage is billed in MCUs too: one MCU covers 5 TB-hours of snapshot, and Morph's own example puts an 8 vCPU, 8 GB RAM, 8 GB disk VM kept as a snapshot at $0.12 a month.

A Fly Machine does not branch. Its nearest feature is suspend, which saves the whole VM state (CPU registers, memory and open file handles) in a Firecracker snapshot and resumes in a few hundred milliseconds. Suspend needs 2 GB of memory or less, so the 4 GB size in the example below cannot use it, and Fly says a deploy, a host migration or maintenance discards the snapshot. A Machine's root disk is temporary; files that must last go on a Fly Volume.

Runtime does both at any size. fork makes 1 to 10 running copies of a sandbox, with its files, memory and processes, and a snapshot keeps the machine to start more copies later, for 7 days unless you choose 1 to 365. See what a sandbox fork is and what a sandbox snapshot is.

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; on Morph, 2 vCPUs and 4 GB is 2 MCUs.

TextMachines  Size   1,000 × 60 s / 3,600 × $0.0861         = $1.44Morph     Size   1,000 × 60 s / 3,600 × 2 MCU × $0.05   = $1.67Runtime   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 $143.50 on Fly Machines, $166.67 on Morph and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $1.44 on Machines and $1.67 on Morph, so Runtime is cheaper however busy the sandbox is. Morph charges an MCU for whichever of CPU, memory or disk a machine needs most of, so a 2 vCPU, 8 GB machine is still 2 MCUs. Plan fees, included credit, storage, network and free credits are left out.

Which one to pick

  • Pick Fly Machines to run a service that stays up, in any of Fly's 18 regions, with volumes and Managed Postgres in the same account, at the lower hourly price of the two.
  • Pick Morph if your agent's search needs hundreds of branches of one running machine at once, or for shareable development boxes that scale to zero and keep their memory.
  • Pick Runtime for forks and pauses that keep memory at any size, measured CPU at $0.025 a vCPU-hour, no plan fee, and an agent that connects without an API key.

Switch from either one

Where you branched a Morph snapshot or kept a warm Machine to copy, prepare one Runtime sandbox and fork it. The copies start running, answered together:

Pythonfrom withruntime import Sandboxwith Sandbox.create(funding="trial") as base:    base.exec("pip install --quiet requests")    forks = base.fork(count=2, funding="trial")  # memory and processes included    for fork in forks:        print(fork.exec("python3 -c 'import requests; print(requests.__version__)'").stdout)        fork.stop()

For one-off jobs, create a sandbox where you created a Machine or an instance, and stop it at the end. 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 compare --from fly-machines (or --from morph) prices what you ran at the old provider's rates, and npx withruntime switch --from fly before your first top-up matches that top-up with credit, up to $100. The full side-by-sides are Runtime vs Fly.io and Runtime vs Morph.

Sources

Rates checked 23 September 2026; the Fly suspend and Morph pricing pages read 25 September 2026.

Facts on this page were checked on 25 September 2026.

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