wasmtime

What it is and what it does

Wasmtime is a Python binding to the Wasmtime WebAssembly runtime, a Bytecode Alliance project that lets you load, compile, and execute WebAssembly modules and components from within Python. It exposes a high-level API for creating stores, modules, instances, and calling exported functions, as well as importing Python functions into WebAssembly. The package ships as a precompiled wheel with no external runtime dependencies, making installation straightforward.

The runtime is actively maintained and follows Wasmtime's versioning scheme, releasing a new major version monthly. This means dependency specifications need regular updates to stay current. It supports modern Python versions (3.9 through 3.14) and PyPy on 64-bit Windows, macOS, and Linux systems. The package is suitable for embedding WebAssembly execution in Python applications, whether for sandboxed computation, plugin systems, or interoperability with WebAssembly-based libraries.

Use it for:

• Execute untrusted or sandboxed WebAssembly code from Python without spawning a separate process.
• Integrate WebAssembly modules compiled from other languages into Python applications.
• Build plugin systems where plugins are distributed as WebAssembly components.
• Call Python functions from within WebAssembly modules via the import interface.
• Prototype or test WebAssembly modules interactively in Python before deployment.

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Embeds the Wasmtime WebAssembly runtime in Python, allowing you to compile, instantiate, and execute WebAssembly modules and components directly from Python code.

Yes. Wasmtime is a mature, actively maintained runtime with low install friction, no runtime dependencies, and broad platform support. The monthly major-version release cycle requires discipline in dependency management, but the package is well-documented and widely used. Install it if you need to execute WebAssembly from Python; verify the license terms for your use case first.

Install

wasmtime on PyPI

pip install wasmtime

uv add wasmtime

poetry add wasmtime

Installing wasmtime

Before you install

Low friction: pure wheel distribution with no runtime dependencies. Actively maintained with releases every month; last commit 2026-07-20. Supports Python 3.9+ on Windows, macOS, and Linux for x86_64 and arm64.

License in practice

Licensed under Apache-2.0 WITH LLVM-exception. License treatment is marked unclear in the metadata, so verify the dual-license terms apply as expected for your use case before relying on it in proprietary or restricted contexts.

Quickstart

pip install wasmtime

from wasmtime import Store, Module, Instance

store = Store()
module = Module(store.engine, "(module (func (export \"test\")))") 
instance = Instance(store, module, [])
test = instance.exports(store)["test"]
test(store)

Requires Python 3.9 or later; 64-bit builds only on Windows, macOS, or Linux with x86_64 or arm64 architecture.

Verify before relying

• Exact scope and stability guarantees of the monthly major-version release cycle for production use.
• Whether the Apache-2.0 WITH LLVM-exception dual-license composition is compatible with your project's license requirements.
• Performance characteristics and memory overhead when executing WebAssembly modules from Python.

Package facts

Evidence: wasmtime-47.0.1-py3-none-any.whl

Tags

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