Compiling a Contract

Within this section, our objective is to retrieve the code for a sample contract and transform it into a wasm binary executable.


Before you proceed, ensure that you have installed the necessary dependencies as detailed in the "Setting Up Environment" guide.

Downloading the Contract

To get started, initiate the download of the cw-contracts repository. The contract we'll be compiling is the nameservice contract.

Clone the following repository:

git clone
cd cw-contracts
git checkout main
cd contracts/nameservice

Compile Contract

In this section, we will go over how to compile using Cargo.

Compile using Cargo

Execute the following command to compile the contract:

cargo wasm

After the compilation process, you should find the file target/wasm32-unknown-unknown/release/cw_nameservice.wasm generated. Its size is roughly 1.9 MB, indicating that it's a release build but hasn't undergone the removal of all redundant code yet. To deploy the contract on-chain, optimization is necessary. Refer to the Optimized Compilation"section below for guidance on optimizing a contract.

Optimized Compilation

In order to minimize gas costs, it is essential to minimize the binary size, resulting in more cost-effective deployment and reduced fees for every interaction. Fortunately, there are available tools to aid in this process. These optimization tools generate reproducible builds of CosmWasm smart contracts, ensuring that third parties can verify the contract's contents as claimed.

Optimize using Cargo

Executing the following command should yield an optimized contract suitable for storage on the blockchain:

RUSTFLAGS='-C link-arg=-s' cargo wasm

Optimize using Rust-Optimizer

You will have needed to already install Docker in order to run the rust-optimizer

Navigate to the project root and run the following command:

docker run --rm -v "$(pwd)":/code \
  --mount type=volume,source="$(basename "$(pwd)")_cache",target=/code/target \
  --mount type=volume,source=registry_cache,target=/usr/local/cargo/registry \

By running this command, the .wasm file will undergo optimization, resulting in an optimized .wasm file located in the artifacts directory. If you have multiple contracts in the workspace append the name of the specific project you want built.

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