Fly.io Machines

Fly.io Machines — Raw Firecracker microVMs with a REST API, durable volumes and 35+ regions. Fly Machines are Firecracker microVMs you start and stop over a REST API, with volumes, private networking and public IPs. Fly does not market this as a sandbox product and ships no agent SDK, so you supply the orchestration layer yourself. In exchange you get regional placement including Sydney, per-second billing, nothing charged while stopped, and pricing roughly an order of magnitude below the agent-native vendors. Built by Fly.io. Founded 2017. Series C.

We track it in 1 comparison — Sandbox providers — so every claim below is a cell in a table you can open and check rather than an impression. Across those rosters it sits against 19 other tools, and what follows is where it visibly separates from them.

Where it wins.

• Price / hour — $0.031 /hr, 2nd of 9.
• Idle cost — free-when-stopped, tied for best across 5 of 16 tools.
• GPU — Yes, which only 3 of 13 tools here manage.
• Sydney region — Yes, which only 3 of 16 tools here manage.
• Funding — series-c-plus, tied for best across 4 of 15 tools.

Each of those is ranked against the whole roster on its category page, not against a hand-picked subset, so a first place here means first of everything we list.

Where it gives ground.

• Runtimes — any-oci-image, 10th of 16. E2B records python, javascript-typescript, bash, any-oci-image.

None of these disqualify it on their own. They are the fields to check against your own requirements before you commit, because they are the ones where a competitor genuinely does better.

Provenance. 25 of 26 tracked fields carry a value for Fly.io Machines, and 10 of those cite a document you can open. Last verified 2026-07-23. Every figure keeps its own provenance — measured by us, claimed by the vendor, inferred, or community-reported — and we would rather print a dash than a guess.

Its nearest neighbour in our data is ascii. Fly.io Machines is ahead on Meter (per-second against subscription) and Custom images (Yes against Partial). That pattern repeats across the rest of the roster — see Fly.io Machines alternatives for the other rivals, each compared the same way.

Company

Fly.io

Founded

2017

Funding

Series C

Fields we track

25 of 26

Last verified

2026-07-23

The best price-per-unit-of-isolation on this page by a wide margin, and the only mainstream option with a Sydney region. You pay for it in glue code: no file API, no exec streaming, no memory fork, no agent SDK. Budget a week to build the layer everyone else sells you.

Cold start

900 ms9th of 16

Inferred

Price / hour

$0.031 /hr2nd of 9

Vendor-claimedverified 2026-07-23source

Idle cost

free-when-stopped1st of 16

Vendor-claimedverified 2026-01-15source

GPU

●Yes1st of 13

Vendor-claimedverified 2026-01-15source

Sydney region

●Yes1st of 16

Vendor-claimedverified 2026-01-15source

Funding

series-c-plus1st of 15

Community-reported

Isolation

microvm1st of 16

Vendor-claimedverified 2026-01-15source

Egress control

allowlist1st of 16

Inferred

Fly.io Machines is the right call in these situations, each one drawn from a field we actually record:

• You need Australian or multi-region placement.
• Cost per sandbox-hour matters more than SDK ergonomics.
• You already run on Fly and can reuse the networking.
• Price / hour is your binding constraint. Fly.io Machines records $0.031 /hr, 2nd of 9 in the Sandbox providers roster. We define that field as list price for roughly 2 vCPU and 4 GB running for one hour on the cheapest paid tier, no commitment, excluding storage and egress.
• Idle cost is your binding constraint. Fly.io Machines records free-when-stopped, the best figure in the Sandbox providers roster. We define that field as what you pay while a sandbox exists but is doing nothing — the common case when an agent is blocked on model inference.
• GPU is your binding constraint. Fly.io Machines records Yes, which only 3 of the 13 tools in the Sandbox providers roster do.
• Sydney region is your binding constraint. Fly.io Machines records Yes, which only 3 of the 16 tools in the Sandbox providers roster do.

Reach for something else when any of the following is a requirement rather than a nice-to-have:

• Runtimes. Fly.io Machines records any-oci-image, 10th of 16 in the Sandbox providers roster. E2B records python, javascript-typescript, bash, any-oci-image on the same field. If that is a hard requirement rather than a preference, start elsewhere.

We publish this block because a comparison that only lists what a tool is good at is marketing. Every figure above sits on the same page as its source, and the field definitions are on the category tables if you want to check how we measured them.

What we don't know. 1 of the 26 fields we track for Fly.io Machines are still blank: GitHub stars. Those render as dashes rather than as zeroes or assumptions, because an empty cell and a bad cell are not the same thing and only one of them is honest. If you know any of these figures and can point at a document, tell us.