CLI Options for wasmtime

The wasmtime CLI is organized into a few subcommands. If no subcommand is provided it'll assume run, which is to execute a wasm file. The subcommands supported by wasmtime are:


This is a general subcommand used to print help information to the terminal. You can execute any number of the following:

$ wasmtime help
$ wasmtime --help
$ wasmtime -h
$ wasmtime help run
$ wasmtime run -h

When in doubt, try running the help command to learn more about functionality!


This is the wasmtime CLI's main subcommand, and it's also the default if no other subcommand is provided. The run command will execute a WebAssembly module. This means that the module will be compiled to native code, instantiated, and then optionally have an export executed.

The wasmtime CLI will automatically hook up any WASI-related imported functionality, but at this time if your module imports anything else it will fail instantiation.

The run command takes one positional argument which is the name of the module to run:

$ wasmtime run foo.wasm
$ wasmtime foo.wasm

Note that the wasmtime CLI can take both a binary WebAssembly file (*.wasm) as well as the text format for WebAssembly (*.wat):

$ wasmtime foo.wat

The run command accepts an optional invoke argument which is the name of an exported function of the module to run.

$ wasmtime run foo.wasm --invoke initialize


The serve subcommand runs a WebAssembly component in the wasi:http/proxy world via the WASI HTTP API, which is available since Wasmtime 18.0.0. The goal of this world is to support sending and receiving HTTP requests.

The serve command takes one positional argument which is the name of the component to run:

$ wasmtime serve foo.wasm

Furthermore, an address can be specified via:

$ wasmtime serve --addr= foo.wasm

At the time of writing, the wasi:http/proxy world is still experimental and requires setup of some wit dependencies. For more information, see the hello-wasi-http example.


The wast command executes a *.wast file which is the test format for the official WebAssembly spec test suite. This subcommand will execute the script file which has a number of directives supported to instantiate modules, link tests, etc.

Executing this looks like:

$ wasmtime wast foo.wast


This subcommand is used to control and edit local Wasmtime configuration settings. The primary purpose of this currently is to configure how Wasmtime's code caching works. You can create a new configuration file for you to edit with:

$ wasmtime config new

And that'll print out the path to the file you can edit.


This subcommand is used to Ahead-Of-Time (AOT) compile a WebAssembly module to produce a "compiled wasm" (.cwasm) file.

The wasmtime run subcommand can then be used to run a AOT-compiled WebAssembly module:

$ wasmtime compile foo.wasm
$ wasmtime foo.cwasm

AOT-compiled modules can be run from hosts that are compatible with the target environment of the AOT-completed module.


This subcommand is used to print the available Cranelift settings for a given target.

When run without options, it will print the settings for the host target and also display what Cranelift settings are inferred for the host:

$ wasmtime settings