A Bytecode Alliance project
CLI and Rust libraries for low-level manipulation of WebAssembly modules
Precompiled artifacts built on CI are available for download for each release.
If you'd prefer to build from source then first install Rust for your platform and then use the included Cargo package manager to install:
$ cargo install wasm-tools
Installation can be confirmed with:
$ wasm-tools --version
Subcommands can be explored with:
$ wasm-tools help
Basic validation/printing:
# Validate a WebAssembly file
$ wasm-tools validate foo.wasm
# Validate a WebAssembly module in the text format, automatically converting to
# binary.
$ wasm-tools validate foo.wat
# Validate a WebAssembly file enabling an off-by-default feature
$ wasm-tools validate foo.wasm --features=exception-handling
# Validate a WebAssembly file with a default-enabled feature disabled
$ wasm-tools validate foo.wasm --features=-simd
# Print the text format of a module to stdout
$ wasm-tools print foo.wasm
# Convert a binary module to text
$ wasm-tools print foo.wasm -o foo.wat
Simple mutation as well as piping commands together:
# Mutate a WebAssembly module and print its text representation to stdout
$ wasm-tools mutate foo.wasm -t
# Mutate a WebAssembly module with a non-default seed and validate that the
# output is a valid module.
$ wasm-tools mutate foo.wasm --seed 192 | wasm-tools validate
# Demangle Rust/C++ symbol names in the `name` section, strip all other custom
# sections, and then print out what binary sections remain.
$ wasm-tools demangle foo.wasm | wasm-tools strip | wasm-tools objdump
Working with components:
# Print the WIT interface of a component
$ wasm-tools component wit component.wasm
# Convert WIT text files to a binary-encoded WIT package, printing the result to
# stdout
$ wasm-tools component wit ./wit -t
# Convert a WIT document to JSON
$ wasm-tools component wit ./wit --json
# Round trip WIT through the binary-encoded format to stdout.
$ wasm-tools component wit ./wit --wasm | wasm-tools component wit
# Convert a core WebAssembly binary into a component. Note that this requires
# WIT metadata having previously been embedded in the core wasm module.
$ wasm-tools component new my-core.wasm -o my-component.wasm
# Convert a core WebAssembly binary which uses WASI to a component.
$ wasm-tools component new my-core.wasm -o my-component.wasm --adapt wasi_snapshot_preview1.reactor.wasm
There are a few conventions that all CLI commands adhere to:
- All subcommands print "short help" with
-h
and "long help" with--help
. - Input is by default read from stdin if no file input is specified (when applicable).
- Output is by default sent to stdout if a
-o
or--output
flag is not provided. Binary WebAssembly is not printed to a tty by default, however. - Commands which output WebAssembly binaries all support a
-t
or--wat
flag to generate the WebAssembly text format instead. - A
-v
or--verbose
flag can be passed to enable log messages throughout the tooling. Verbosity can be turned up by passing the flag multiple times such as-vvv
. - Color in error messages and console output is enabled by default for TTY based
outputs and can be configured with a
--color
argument.
The wasm-tools
binary internally contains a number of subcommands for working
with wasm modules and component. Many subcommands also come with Rust crates
that can be use programmatically as well:
CLI | Rust Crate | Description |
---|---|---|
wasm-tools validate |
wasmparser | Validate a WebAssembly file |
wasm-tools parse |
wat and wast | Translate the WebAssembly text format to binary |
wasm-tools print |
wasmprinter | Translate the WebAssembly binary format to text |
wasm-tools smith |
wasm-smith | Generate a valid WebAssembly module from an input seed |
wasm-tools mutate |
wasm-mutate | Mutate an input wasm file into a new valid wasm file |
wasm-tools shrink |
wasm-shrink | Shrink a wasm file while preserving a predicate |
wasm-tools dump |
Print debugging information about the binary format | |
wasm-tools objdump |
Print debugging information about section headers | |
wasm-tools strip |
Remove custom sections from a WebAssembly file | |
wasm-tools demangle |
Demangle Rust and C++ symbol names in the name section |
|
wasm-tools compose |
wasm-compose | Compose wasm components together |
wasm-tools component new |
wit-component | Create a component from a core wasm binary |
wasm-tools component wit |
Extract a *.wit interface from a component |
|
wasm-tools component embed |
Embed a component-type custom section in a core wasm binary |
|
wasm-tools metadata show |
wasm-metadata | Show name and producer metadata in a component or module |
wasm-tools metadata add |
Add name or producer metadata to a component or module | |
wasm-tools addr2line |
Translate wasm offsets to filename/line numbers with DWARF | |
wasm-tools completion |
Generate shell completion scripts for wasm-tools |
The wasm-tools
CLI contains useful tools for debugging WebAssembly modules and
components. The various subcommands all have --help
explainer texts to
describe more about their functionality as well.
As mentioned above many of the tools of the wasm-tools
CLI have libraries
implemented in this repository as well. These libraries are:
wasmparser
- a library to parse WebAssembly binarieswat
- a library to parse the WebAssembly text formatwast
- likewat
, except provides an ASTwasmprinter
- prints WebAssembly binaries in their string formwasm-mutate
- a WebAssembly test case mutatorwasm-shrink
- a WebAssembly test case shrinkerwasm-smith
- a WebAssembly test case generatorwasm-encoder
- a crate to generate a binary WebAssembly modulewit-parser
- a crate to parse and manage*.wit
files and interfaces.wit-component
- a crate to create components from core wasm modules.wasm-metadata
- a crate to manipulate name and producer metadata (custom sections) in a wasm module or component.
It's recommended to use the libraries directly rather than the CLI tooling when embedding into a separate project.
Using the CMakeLists.txt
in crates/c-api
, wasm-tools
can be used from the
wasm-tools.h
header. Note that these
bindings do not comprehensively cover all the functionality of this repository
at this time, but please feel free to contribute more if you find functions
useful!
This repository has both a CLI and a suite of crates that is published to crates.io (Rust's package manager). The versioning scheme used by this repository looks like:
wasm-tools
- the CLI follows the versioning pattern of1.X.Y
. FrequentlyY
is 0 andX
is bumped as part of a release for this repository.wat
- this Rust crate is versioned at1.X.Y
as well and matches thewasm-tools
version.wast
- this Rust crate is versioned asX.0.Y
. TheX
here matches theX
in1.X.Y
ofwasm-tools
.- All other crates - all other crates in this repository are versioned at
0.X.Y
whereX
matches the1.X.Y
ofwasm-tools
.
Note that the Y
of all the versions above will also match for any release of
this repository. This versioning scheme is intended to reflect the stable nature
of the CLI and the wat
crate in terms of API stability. Other crates, however,
all receive a major version bump that are not automatically considered API
compatible on all releases. This reflects how WebAssembly itself is an evolving
standard which is not an unchanging foundation. All of the crates in this
repository are suitable for "production use" but be aware that API stability is
not guaranteed over time. If you have difficulty upgrading versions please feel
free to file an issue and we can help out.
Also, this repository does not currently have a strict release cadence. Releases are done on an as-needed basis. If you'd like a release done please feel free to reach out on Zulip, file an issue, leave a comment on a PR, or otherwise contact a maintainer.
For maintainers, the release process looks like:
- Go to this link
- Click on "Run workflow" in the UI.
- Use the default
bump
argument and hit "Run workflow" - Wait for a PR to be created by CI. You can watch the "Actions" tab for if things go wrong.
- When the PR opens, close it then reopen it. Don't ask questions.
- Review the PR, approve it, then queue it for merge.
That should be it, but be sure to keep an eye on CI in case anything goes wrong.
See CONTRIBUTING.md for more information about contributing to this repository.
This project is licensed under the Apache 2.0 license with the LLVM exception. See LICENSE for more details.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.