# Wasmtime: a WebAssembly Runtime.
Wasmtime is a standalone wasm-only runtime for [WebAssembly], using the [Cranelift] JIT.
It runs WebAssembly code [outside of the Web], and can be used both as a command-line
utility or as a library embedded in a larger application.
[WebAssembly]: https://webassembly.org/
[Cranelift]: https://github.com/CraneStation/cranelift
[outside of the Web]: https://webassembly.org/docs/non-web/
[](https://dev.azure.com/CraneStation/Wasmtime/_build/latest?definitionId=4&branchName=master)
[](https://gitter.im/CraneStation/Lobby)
Wasmtime passes the WebAssembly spec testsuite, and supports a new system
API proposal called [WebAssembly System Interface], or WASI.
Wasmtime includes a git submodule; in order to build it, it's necessary to
obtain a full checkout, like this:
```
git clone --recurse-submodules https://github.com/CraneStation/wasmtime.git
```
To build an optimized version of Wasmtime, use Cargo:
```
cargo build --release
```
There are Rust, C, and C++ toolchains that can compile programs with WASI. See
the [WASI intro][WASI intro] for more information, and the [WASI tutorial][WASI tutorial]
for a tutorial on compiling and running programs using WASI and wasmtime, as
well as an overview of the filesystem sandboxing system.
Wasmtime does not yet implement Spectre mitigations, however this is a subject
of ongoing research.
[CloudABI]: https://cloudabi.org/
[WebAssembly System Interface]: docs/WASI-overview.md
[WASI intro]: docs/WASI-intro.md
[WASI tutorial]: docs/WASI-tutorial.md
Additional goals for Wasmtime include:
- Support a variety of host APIs (not just WASI Core), with fast calling sequences,
and develop proposals for additional API modules to be part of WASI.
[Reference Sysroot](https://github.com/WebAssembly/reference-sysroot).
- Implement the [proposed WebAssembly C API].
- Facilitate testing, experimentation, and development around the [Cranelift] and
[Lightbeam] JITs.
- Develop a native ABI used for compiling WebAssembly suitable for use in both
JIT and AOT to native object files.
[proposed WebAssembly C API]: https://github.com/rossberg/wasm-c-api
[Cranelift]: https://github.com/CraneStation/cranelift
[Lightbeam]: https://github.com/CraneStation/lightbeam
#### Including Wasmtime in your project
Wasmtime exposes an API for JIT compilation through the `wasmtime-jit` subcrate, which depends on `wasmtime-environ` and `wasmtime-runtime` for the ABI and runtime support respectively. However, this API is not documented and subject to change. Please use at your own risk!
Build the individual crates as such:
```
cargo build --package wasmtime-jit
```
Wasmtime does not currently publish these crates on crates.io. They may be included as a git dependency, like this:
```toml
[dependencies]
wasmtime-environ = { git = "https://github.com/CraneStation/wasmtime", rev = "somecommithash" }
wasmtime-runtime = { git = "https://github.com/CraneStation/wasmtime", rev = "somecommithash" }
wasmtime-jit = { git = "https://github.com/CraneStation/wasmtime", rev = "somecommithash" }
```
All three crates must be specified as dependencies for `wasmtime-jit` to build correctly, at the moment.
It's Wasmtime.