ERC-223 is a technical standard for token implementation using smart contracts on the Ethereum blockchain. ERC-223 tokens serve a purpose similar to and seek to improve up ERC-20 tokens. While ubiquitous, ERC-20 tokens are vulnerable in that may be permanently ‘lost’ should they be accidentally sent to a smart contract not intended to receive them. In contrast, ERC-223 tokens include a mechanism that returns them to their original address in the event a contract is unprepared to receive them. Additionally, ERC-223 tokens are backwards compatible with ERC-20 tokens, while typically requiring only half as much gas, as only one function, rather than two, must be called to initiate and complete a transaction. The framework for ERC-223 tokens was first published as part of an Ethereum Improvement Proposal in 2017.