Wasmer
An MIT-licensed WebAssembly runtime and WASIX ecosystem that runs registry packages such as Python, Bash and PHP in local sandboxes, with Wasmer Edge as the hosted option. A practical way to embed interpreter sandboxes in JS or Python apps; pick Wasmtime for a pure engine and a hosted VM sandbox for full Linux.
Overview
Wasmer is a WebAssembly runtime and CLI, MIT-licensed, that "runs your apps in fast, secure, and lightweight sandboxes: locally, in the cloud, or in your browser". The company, backed by Y Combinator, pairs the runtime with a registry of ready-to-run packages (Bash, PHP, Python, Node.js, PGlite, SQLite, curl, FFmpeg, Pandoc) and WASIX, its superset of WASI. The runtime is "Secure by default. No file, network, or environment access, unless explicitly enabled", offers Singlepass, Cranelift and LLVM backends plus browser and V8 integration backends, and installs on macOS, Linux and Windows; wasmer run python/python starts a sandboxed Python. The separate wasmer-sdk "turns packages from the Wasmer registry into composable sandboxes" from JavaScript (Node.js 20+ and browsers), Python, Rust and a Swift preview, and is "currently alpha".
Wasmer Edge is the hosted side: a platform "powered by WebAssembly, Wasmer, and WASIX" that runs stateless HTTP workloads close to users, with volumes, cron jobs, wasmer ssh sessions and rollback, and always-on workloads in development. The Hobby plan is free for non-commercial use and Pro is $10 per month with usage overages; Enterprise adds subhosting, private locations and a 99.95% SLA. Wasmer sells this as "Universal compute. Built for AI", but the pages checked do not describe an agent-specific sandbox API. Wasmer v7.5.0 was released on 1 October 2026. Because everything runs as Wasm, native packages that are not in the registry or compiled to WASIX are out of reach.
Notable
- Runtime is MIT-licensed; v7.5.0 released 1 October 2026; about 21,000 GitHub stars
- Backed by Y Combinator; Wasmer Edge Pro is $10/month, Hobby is free with 12 global regions
- wasmer-sdk (JavaScript, Python, Rust, Swift) is labelled alpha
Wasmer specifications
| Attribute | Details |
|---|---|
| Isolation | WebAssembly sandbox per package; "No file, network, or environment access, unless explicitly enabled"; WASIX extends WASI with POSIX-style features |
| Deployment | Open-source project · Self-hostable |
| Open source | Yes (MIT) |
| SDKs and interfaces | CLI, JavaScript/TypeScript, Python, Rust, Swift |
| Cold start (vendor claim) | Home page claims 107x faster cold starts and 51x less memory per instance than VPS or VM alternatives, based on Wasmer's own comparison model; no absolute figure |
| Max session length | Not documented |
| Persistence | Wasmer Edge offers persistent volumes, remote sessions via wasmer ssh and app versioning with rollback; the runtime itself has no snapshotting |
| GPU | No - CPU-only WebAssembly execution |
| Networking | Disabled unless explicitly enabled; WASIX networking in the runtime, and in the JavaScript SDK Node.js networking is bridged through node:net and node:dns |
| Pricing | Runtime free and open source. Wasmer Edge: Hobby free; Pro $10/month with overages of $0.50 per million requests, $0.10 per GB bandwidth, $0.10 per active CPU hour, $0.01 per GB-hour memory, $0.05 per GB storage; Enterprise and subhosting custom |
| Free tier | Free to self-host; Wasmer Edge Hobby plan free for personal non-commercial projects: 100 apps, 1,000,000 requests, 150 GB bandwidth, 6 active CPU hours and 400 GB-hours memory per month |
| Compliance | Not documented |
| Regions | Wasmer Edge: 12 global regions on Hobby and Pro; private dedicated locations on Enterprise |
Facts from Wasmer’s public documentation, verified November 9, 2026. Performance numbers are vendor claims.
Strengths and trade-offs
Strengths
- You want to run a sandboxed Python or Bash interpreter inside a JavaScript or Python process, including in the browser
- You need a runtime that installs on macOS, Windows and Linux without a hypervisor
- You want a hosted path (Wasmer Edge) with a free tier and published overage rates
Trade-offs
- Only packages compiled to Wasm/WASIX run; arbitrary native dependencies are unavailable
- The sandbox SDK is alpha and its API may change
- Wasmer Edge is stateless HTTP by default; TCP/UDP and always-on workloads require contacting the team or are in development
- Cold-start and memory claims on the home page are relative to Wasmer's own comparison model
Good fit for: Running interpreter packages (Python, PHP, Bash) in Wasm sandboxes from JavaScript or Python, locally, in the browser or on Wasmer Edge.
How Wasmer compares
| Sandbox | Isolation | Open source | Self-host / BYOC | Cold start (vendor) | Max session | Snapshots / pause | GPU | SDKs |
|---|---|---|---|---|---|---|---|---|
| Wasmer | Wasm sandbox | Yes | Yes / No | Not documented | Not documented | Not documented / Not documented | No | CLI, JavaScript/TypeScript, Python, Rust, Swift |
| Wasmtime | Wasm sandbox | Yes | Yes / No | Not documented | Embedder-set | No / Not documented | No | CLI, Rust, C, C++, Python, .NET, Go, Ruby |
| Spin (Fermyon) | Wasm component | Yes | Yes / No | ms (claim) | 30 s (Fermyon Cloud) | No / No | No | CLI, Rust, JavaScript/TypeScript, Go, Python |
| Pyodide | CPython in Wasm | Yes | Yes / No | Not documented | Not documented | No / No | No | JavaScript/TypeScript, Python |
| Extism | Wasm plug-in sandbox | Yes | Yes / No | Not documented | Host-set | No / No | No | Rust, JavaScript/TypeScript, Go, Python, Ruby, .NET, Java, PHP, Elixir, Haskell, OCaml, Perl, Zig, C, C++ |
| Cloudflare Sandbox SDK | MicroVM (Containers) | Yes | No / No | 1–3 s | No fixed cap | Yes / Not documented | Not documented | TypeScript (Workers) |
Frequently asked questions
What is Wasmer?
How does Wasmer isolate code?
Is Wasmer open source?
How much does Wasmer cost?
What are the alternatives to Wasmer?
Sources
Cite this page
Agent Sandboxes. (2026). Wasmer. agentsandboxes.org. Last reviewed November 9, 2026. https://agentsandboxes.org/sandboxes/wasmer/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.