ERC-2981

The standard centers on a single function: royaltyInfo(tokenId, salePrice), which returns the receiver address and the amount due. At the point of sale, the marketplace calls it with the price and learns whom and how much to pay. ERC-2981 does not enforce the payment on-chain. The specification states this plainly: payment is voluntary, because transfer mechanisms such as transferFrom do not always imply a sale. The standard normalizes how to retrieve the information, not how to force the payment. It is compatible with ERC-721 and ERC-1155, though it does not require that compatibility.

The EIP-2981 specification, Final in status, was created on 15 September 2020 and finalized in July 2021, authored by Zach Burks, James Morgan, Blaine Malone and James Seibel. It requires ERC-165 and its interface identifier is 0x2a55205a. It matters because each marketplace used to handle royalties in proprietary, incompatible ways; ERC-2981 unifies that signal across platforms.

The citable nuance of ERC-2981 is its voluntary nature, the structural reason behind the later debate over how to apply royalties off-chain. It is a layer mounted on ERC-721 or ERC-1155. It is useful for grasping a principle that carries over to real-world asset tokenization and compliance: a rule written into a smart contract does not guarantee its economic execution when it depends on an external actor. The good practice is to design the operating model around that limit from the start.