Fly.io

license

Proprietary

service

proprietary(Fly.io managed)

source

closed

clients

CLI/REST/JS/Go SDKs (client libs only, no open runtime)

isolation

Firecracker(Firecracker itself is OSS/AWS, but the Sprites product/orchestration is proprietary)

Fly Sprites is a proprietary managed sandbox SaaS; only client SDKs are open, not the runtime. The underlying Firecracker hypervisor is open source, but Fly.io's orchestration and control plane are closed, sold as metered usage with no self-hostable release.

• https://fly.io/legal/terms-of-service/ recorded 2026-09-29

  Terms of service state that "Fly.io retains all right, title and interest in and to the Documentation and all software and all Fly.io proprietary information and technology" and that "no license or other rights in the Fly.io Technology are granted to Customer".

• https://sprites.dev/ recorded 2026-08-13

  Sprites = hardware-isolated Firecracker execution env for arbitrary code; managed service, CLI/REST/JS/Go clients; no self-hostable open runtime

Fly.io discloses no user, customer, session or Sprite count for Sprites; the only figures on the product page are its per-CPU-hour and per-GB-hour prices. With no usage signal to read, adoption here reflects that absence rather than any confirmed traction.

• https://fly.io/sprites recorded 2026-09-29

  Searched the Sprites product page body for user, customer, session and Sprite counts: none; the only figures are pricing, "CPU at $0.07/CPU-hour, RAM at $0.04375/GB-hour".

• https://simonwillison.net/2026/Jan/9/sprites-dev/ recorded 2026-08-13

  Sprites launched early Jan 2026 as Fly.io's E2B competitor (corroborating recency, not a usage figure)

• https://sprites.dev/ recorded 2026-08-13

  product live, usage-based pricing ($0.07/CPU-hr); no user/customer figures disclosed

Each Sprite is a Firecracker microVM with its own kernel, isolated in hardware, with a persistent 100 GB volume that survives sleep and moves between hosts, plus live copy-on-write checkpoints. What keeps it a step below the frontier is scale: the product is new and unproven against established incumbents, and Fly.io no longer publishes a bounded cold-start figure.

• https://docs.sprites.dev/ recorded 2026-09-29

  The Sprites docs overview lists isolation as "Hardware-level" with "dedicated microVM", and says "Every Sprite has a persistent, standard ext4 filesystem".

• https://fly.io/agents-need-a-computer/ recorded 2026-09-29

  The page states "A Sprite is exactly that: a Firecracker microVM with its own kernel and a durable Linux filesystem, one agent to a box, isolated in hardware from every other Sprite".

• https://fly.io/sprites recorded 2026-09-29

  The Sprites page describes "The volume is 100 GB" as a normal POSIX filesystem, checkpoints that "Snapshot the whole filesystem in about a second", and plan limits where "Hero allows 100 concurrently running sprites and 100 warm sprites; cold sprites are unlimited".

• https://sprites.dev/ recorded 2026-08-13

  persistent 100 GB ext4/POSIX volume surviving sleep and machine moves, live copy-on-write checkpoint and restore, arbitrary Linux code, usage-metered pricing; no isolation mechanism or latency figure stated