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Spin (Fermyon)

Answer in brief

A CNCF sandbox framework for event-driven WebAssembly component apps on Wasmtime, created by Fermyon (now Akamai) and hosted as Fermyon Cloud and Akamai Functions. Choose Spin for Wasm-isolated function endpoints you can run anywhere; not a general code-execution sandbox.

By the Agent Sandboxes editors · Updated

Overview

Spin is "an open source framework for building and running fast, secure, and composable cloud microservices with WebAssembly", licensed Apache-2.0 and "an open source Cloud Native Computing Foundation sandbox project". It "takes advantage of the latest developments in the WebAssembly component model and Wasmtime runtime": you write an HTTP or Redis-triggered handler in Rust, JavaScript/TypeScript, Go or Python (the framework team supports those four SDKs; Zig and MoonBit are third-party), compile it to a wasm32-wasip2 component, and run it with the spin CLI locally, on your own servers, on Kubernetes through SpinKube, or on a hosted service. Spin v4.3.0 was released on 5 November 2026.

Fermyon Technologies, which created Spin, was acquired by Akamai; Akamai's press release of 1 December 2025 says it "has acquired Fermyon the serverless WebAssembly company" and that it will continue to support the Spin and SpinKube CNCF projects, with co-founders Matt Butcher and Radu Matei leading them from Akamai's Cloud Technology Group. Two hosted targets exist: Fermyon Cloud, "currently an open beta service" with no SLA, whose Starter plan allows 5 apps, 100,000 requests a month and 30-second handlers; and Akamai Functions (formerly Fermyon Wasm Functions), a "globally distributed PaaS" built on Spin, in public preview by request and deployed with spin aka deploy. As a function framework, Spin is a building block for tool endpoints rather than a workspace: handlers are short-lived, stateless and limited to languages that compile to Wasm components.

Notable

  • CNCF sandbox project; Apache-2.0; Spin v4.3.0 released 5 November 2026
  • Akamai announced its acquisition of Fermyon on 1 December 2025 and committed to continue supporting Spin and SpinKube
  • Fermyon Cloud is an open beta with no SLA; Akamai Functions is in public preview by request

Spin (Fermyon) specifications

AttributeDetails
IsolationWebAssembly component per handler on the Wasmtime runtime; Akamai Functions describes "a Wasmtime-based runtime with strong isolation and memory safety"
DeploymentOpen-source project · Self-hostable
Open sourceYes (Apache-2.0)
SDKs and interfacesCLI, Rust, JavaScript/TypeScript, Go, Python
Cold start (vendor claim)spinframework.dev describes Wasm as having "millisecond cold starts"; Akamai Functions claims "zero cold starts" and "sub-millisecond startup" without benchmarks
Max session lengthUnlimited self-hosted; Fermyon Cloud Starter caps request handler duration at 30 seconds
PersistenceStateless handlers; Fermyon Cloud provides key-value stores and SQLite databases (Starter: 5 stores at 1 GB total, 1 database up to 1 GB)
GPUNo - Wasm components are CPU-only
NetworkingOutbound HTTP from components via the Spin SDKs; Fermyon Cloud Starter allows 500 outbound requests per hour per app
PricingSpin: free and open source. Fermyon Cloud: Starter, Growth and Enterprise plans (prices not on the FAQ page checked). Akamai Functions: public preview by request; pricing not published
Free tierFree to self-host; Fermyon Cloud Starter: 5 apps, 100,000 requests per month, 5 GB egress, 1 region
ComplianceNot documented
RegionsNot documented

Facts from Spin (Fermyon)’s public documentation, verified November 9, 2026. Performance numbers are vendor claims.

Strengths and trade-offs

Strengths

  • You want millisecond-start serverless functions in Wasm with a local-first CLI workflow
  • You run Kubernetes and want the same components deployed via SpinKube
  • You need a hosted option with a free tier (Fermyon Cloud Starter) or an edge platform (Akamai Functions)

Trade-offs

  • Handlers are stateless and short-lived (30 s on Fermyon Cloud Starter); not a workspace for a coding agent
  • Only languages with Wasm component toolchains; no native packages
  • Hosted offerings are beta or preview with unpublished pricing, and ownership changed to Akamai in late 2025
  • No GPU

Good fit for: Serverless HTTP functions compiled to Wasm components, run locally with the Spin CLI or on Fermyon Cloud, SpinKube or Akamai.

How Spin (Fermyon) compares

SandboxIsolationOpen sourceSelf-host / BYOCCold start (vendor)Max sessionSnapshots / pauseGPUSDKs
Spin (Fermyon)Wasm componentYesYes / Noms (claim)30 s (Fermyon Cloud)No / NoNoCLI, Rust, JavaScript/TypeScript, Go, Python
WasmtimeWasm sandboxYesYes / NoNot documentedEmbedder-setNo / Not documentedNoCLI, Rust, C, C++, Python, .NET, Go, Ruby
WasmerWasm sandboxYesYes / NoNot documentedNot documentedNot documented / Not documentedNoCLI, JavaScript/TypeScript, Python, Rust, Swift
ExtismWasm plug-in sandboxYesYes / NoNot documentedHost-setNo / NoNoRust, JavaScript/TypeScript, Go, Python, Ruby, .NET, Java, PHP, Elixir, Haskell, OCaml, Perl, Zig, C, C++
Cloudflare Sandbox SDKMicroVM (Containers)YesNo / No1–3 sNo fixed capYes / Not documentedNot documentedTypeScript (Workers)
Fly MachinesFirecracker microVMNoNo / No<1 s start (claimed)Not documentedYes / YesNot documentedGo, CLI, REST API

See all Spin (Fermyon) alternatives →

Frequently asked questions

What is Spin (Fermyon)?
A CNCF sandbox framework for event-driven WebAssembly component apps on Wasmtime, created by Fermyon (now Akamai) and hosted as Fermyon Cloud and Akamai Functions. Choose Spin for Wasm-isolated function endpoints you can run anywhere; not a general code-execution sandbox.
How does Spin (Fermyon) isolate code?
Spin (Fermyon) documents its isolation as: WebAssembly component per handler on the Wasmtime runtime; Akamai Functions describes "a Wasmtime-based runtime with strong isolation and memory safety".
Is Spin (Fermyon) open source?
Yes (Apache-2.0). It can be self-hosted.
How much does Spin (Fermyon) cost?
Spin: free and open source. Fermyon Cloud: Starter, Growth and Enterprise plans (prices not on the FAQ page checked). Akamai Functions: public preview by request; pricing not published Check the official pricing page for current rates.
What are the alternatives to Spin (Fermyon)?
Common alternatives include Wasmtime, Wasmer, Extism, Cloudflare Sandbox SDK, Fly Machines. See Spin (Fermyon) alternatives for a full comparison.

Sources

  1. spinframework.dev
  2. github.com/spinframework/spin
  3. github.com/spinframework/spin/releases
  4. akamai.com/newsroom/press-release/akamai-announces-acquisition-of-function-as-a-service-company-fermyon
  5. akamai.com/products/akamai-functions
  6. techdocs.akamai.com/akamai-functions/docs/welcome
  7. developer.fermyon.com/cloud/index
  8. developer.fermyon.com/cloud/faq

Cite this page

Agent Sandboxes. (2026). Spin (Fermyon). agentsandboxes.org. Last reviewed November 9, 2026. https://agentsandboxes.org/sandboxes/fermyon-spin/

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