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Version: v6

Use Solidity tooling

Use ink! with Solidity ABI

ink! v6 contracts can be configured to use Solidity ABI encoding, enabling seamless compatibility with Ethereum tools like MetaMask, Hardhat, Wagmi, and ethers.js. This allows you to leverage the Ethereum ecosystem while building on Polkadot networks.

Why Use Solidity ABI?​

By enabling Solidity ABI compatibility, you can:

  • Use Ethereum wallets like MetaMask to interact with your ink! contracts
  • Deploy with Hardhat and other familiar Ethereum development tools
  • Build frontends using ethers.js, Wagmi, and React hooks
  • Call Solidity contracts from ink! and vice versa
  • Share contracts easily with Ethereum developers

Quick Start​

1. Create Your Contract​

pop new contract my_contract -t standard
cd my_contract

2. Enable Solidity ABI​

Open Cargo.toml, add the ink-lang table under [package.metadata], and configure the ABI mode:

[package.metadata.ink-lang]
abi = "sol"

Setting abi = "sol" puts the contract into Solidity ABI compatibility mode, so all constructor, message, and event types must translate to Solidity ABI types. See the Type Reference for supported mappings.

3. Build with Solidity Metadata​

pop build --release --metadata solidity

This generates Solidity-compatible artifacts in target/ink/:

  • *.abi - Solidity ABI file for contract interaction
  • *.json - Metadata compatible with Ethereum tooling

How It Works​

When you specify abi = "sol", the ink! code generator follows the Solidity ABI specification:

Function Selectors​

  • Message selectors use keccak256 hashing (Ethereum standard)
  • First 4 bytes of keccak256("functionName(type1,type2,...)")
  • Manual selector overrides via #[ink(selector = ...)] are ignored

Encoding/Decoding​

  • Uses Solidity ABI encoding for inputs/outputs
  • Events and errors follow Solidity format
  • Internal storage still uses SCALE codec (no storage changes!)

Constraints​

  • Only one constructor can be defined
  • All types must map to Solidity ABI types (see Type Reference)
  • Call builders are generated for Solidity calling conventions
Storage Format

The contract ABI only affects external interactions. Your contract's internal storage remains SCALE-encoded! Using Solidity ABI does not change your storage layout.

Dual ABI Mode ("all")​

You can support both ink! and Solidity ABIs simultaneously:

[package.metadata.ink-lang]
abi = "all"

Benefits​

  • Contracts callable by both ink! and Solidity tools
  • Each message has two entry points (ink! selector + Solidity selector)
  • Flexibility for cross-ecosystem interoperability

Tradeoffs​

  • Larger contract size (both entry points compiled in)
  • Must designate a #[ink(constructor, default)] for Solidity instantiation
  • All types must be Solidity-compatible
#[ink(constructor, default)]
pub fn new(initial_value: bool) -> Self {
    Self { value: initial_value }
}
Type Requirements

The "all" ABI mode requires all message arguments, return types, and event arguments to be mappable to Solidity ABI types. See the Type Reference for details.

Next Steps​

Now that your contract uses Solidity ABI: