There are two GN target templates which should be used for Rust projects:

The examples/rust directory has some examples of Rust packages that use these targets, as do the Rust FIDL examples.

Building with a custom toolchain

If you want to test out Fuchsia with your own custom-built versions of rustc or cargo, you can set the rustc_prefix argument to fx set, like this:

fx set core.x64 --release --args "rustc_prefix=\"/path/to/bin/dir\""


Fuchsia Rust targets are not built with Cargo during a normal build, and as such, do not require Cargo.toml files. However, having a Cargo.toml file for your target is useful for integration with IDEs such as Intellij and VS Code, and for using the fargo tool to build and test targets without going through a full GN build and run cycle each time.

A Cargo.toml file can be automatically generated for rustc_library and rustc_binary targets based on their .gn file definitions by running:

fx build path/from/fuchsia_/root/to/target:label_cargo
fx gen-cargo path/from/fuchsia/root/to/target:label

Note that the label you use must be the GN label for a rustc_... GN template invocation, not a Fuchsia package or other GN rule.

Or, if you're already in a directory with a single Rust target:

fx gen-cargo .

Autogenerated docs

You can generate and browse HTML documentation for your target and its dependencies by running:

fx rustdoc path/from/fuchsia/root/to/target:label --open


You can run unit tests on connected devices using fx, with the fx test {package name} command. See Testing Rust code for information on adding and running tests.

Warnings & Errors

By default our build configuration makes all Rust warnings into errors. This requirement can be onerous during development, and on your local machine you may wish to see warnings as warnings and let CQ enforce the hard boundary.

The rust_cap_lints GN arg allows you to control this behavior in your development environment. Setting rust_cap_lints = "warn" in fx args or fx set will allow you to develop locally without being blocked by warnings.


We don't currently have a style guide for Rust, but you should run fx rustfmt or fx format-code before submitting. We mostly use the rustfmt defaults, but have a couple custom settings.

Rust Idiomatic Usage Review

If you're new to Rust, and would like someone to review your changes to validate that your usage of Rust is idiomatic, contact one of the following (or add them as a reviewer to your change.)


(To volunteer for this, please add yourself to the list above and upload the change with one of the above as the reviewer).

Communication channels

Public discussion happens on the mailing list. For Googler-only channels, see go/fuchsia-rust-googlers.

Existing Fuchsia Rust libraries

Going further