WebAssembly is a way to safely run code compiled in other languages. Runtimes execute WebAssembly Modules (Wasm), which are most often binaries with a .wasm extension.

wazero is a WebAssembly Core Specification 1.0 and 2.0 compliant runtime written in Go. It has zero dependencies, and doesn't rely on CGO. This means you can run applications in other languages and still keep cross compilation.

Import wazero and extend your Go application with code written in any language!

The best way to learn wazero is by trying one of our examples. The most basic example extends a Go application with an addition function defined in WebAssembly.

There are two runtime configurations supported in wazero: Compiler is default:

By default, ex wazero.NewRuntime(ctx), the Compiler is used if supported. You can also force the interpreter like so:

r := wazero.NewRuntimeWithConfig(ctx, wazero.NewRuntimeConfigInterpreter())

Interpreter is a naive interpreter-based implementation of Wasm virtual machine. Its implementation doesn't have any platform (GOARCH, GOOS) specific code, therefore interpreter can be used for any compilation target available for Go (such as riscv64).

Compiler compiles WebAssembly modules into machine code ahead of time (AOT), during Runtime.CompileModule. This means your WebAssembly functions execute natively at runtime. Compiler is faster than Interpreter, often by order of magnitude (10x) or more. This is done without host-specific dependencies.

If interested, check out the RATIONALE.md and help us optimize further!

Both runtimes pass WebAssembly Core 1.0 and 2.0 specification tests on supported platforms:

The below support policy focuses on compatability concerns of those embedding wazero into their Go applications.

wazero is an early project, so APIs are subject to change until version 1.0. To use wazero meanwhile, you need to use the latest pre-release like this:

go get github.com/tetratelabs/wazero@latest

wazero will tag a new pre-release at least once a month until 1.0. 1.0 is scheduled for Feb 2023, following the release of Go 1.20. wazero 1.0 will build with Go 1.18 and above per the below policy.

Meanwhile, please practice the current APIs to ensure they work for you, and give us a star if you are enjoying it so far!

wazero has no dependencies except Go, so the only source of conflict in your project's use of wazero is the Go version.

wazero follows the same version policy as Go's Release Policy: two versions. wazero will ensure these versions work and bugs are valid if there's an issue with a current Go version.

Additionally, wazero intentionally delays usage of language or standard library features one additional version. For example, when Go 1.29 is released, wazero can use language features or standard libraries added in 1.27. This is a convenience for embedders who have a slower version policy than Go. However, only supported Go versions may be used to raise support issues.

wazero has two runtime modes: Interpreter and Compiler. The only supported operating systems are ones we test, but that doesn't necessarily mean other operating system versions won't work.

We currently test Linux (Ubuntu and scratch), MacOS and Windows as packaged by GitHub Actions, as well FreeBSD via Vagrant/VirtualBox.

• Interpreter
  • Linux is tested on amd64 (native) as well arm64 and riscv64 via emulation.
  • FreeBSD, MacOS and Windows are only tested on amd64.
• Compiler
  • Linux is tested on amd64 (native) as well arm64 via emulation.
  • FreeBSD, MacOS and Windows are only tested on amd64.

wazero has no dependencies and doesn't require CGO. This means it can also be embedded in an application that doesn't use an operating system. This is a main differentiator between wazero and alternatives.

We verify zero dependencies by running tests in Docker's scratch image. This approach ensures compatibility with any parent image.

wazero is a registered trademark of Tetrate.io, Inc. in the United States and/or other countries