Compile a Rust smart contract module#

This guide will show you how to compile smart contract module written in Rust to a Wasm module.


Make sure to have Rust and Cargo installed and the wasm32-unknown-unknown target, together with cargo-concordium and the Rust source code for a smart contract module, you wish to compile.

See also

For instructions on how to install the developer tools see Install tools for development.

Compiling to Wasm#

To help building smart contract modules and to take advantage of features such as contract schemas, Concordium recommends using the cargo-concordium tool for building Rust smart contracts.

In order to build a smart contract, run:

$cargo concordium build

This uses Cargo for building, but runs further optimizations on the result.

If you want a smaller code footprint, enable the wee_alloc feature by using:

$cargo concordium build --features wee_alloc

See also

For building the schema for a smart contract module, some further preparation is required.


It is also possible to compile using Cargo directly by running:

$cargo build --target=wasm32-unknown-unknown [--release]

Note that even with --release set, the produced Wasm module includes debug information.

Running the cargo concordium build command will produce a smart contract module which can be found relative to your project root folder in ./target/concordium/wasm32-unknown-unknown/release/my_module.wasm.v1. Alternatively, you can supply the location where to store the smart contract module using the --out option. For example running the following command will output your smart contract module into the root folder of your project in a file name my_module.wasm.v1.

$cargo concordium build --out ./my_module.wasm.v1


cargo-concordium produces several smart contract modules with different suffixes. The suffix corresponds to the smart contract version, i.e. my_module.wasm/my_module.wasm.v0 for V0 contracts and my_module.wasm.v1 for V1 contracts. Concordium recommends using the wasm module with the .v1 extension (the most-up-to date smart contract version). The file my_module.wasm.v1 will be used when deploying a smart contract on-chain.