This draft standardizes a canonical ownerOf(uint256) read for non-fungible
ERC-1155 and ERC-6909 token IDs — IDs whose supply is fixed to one.
ERC-1155 and ERC-6909 expose balances by (owner, id), but neither offers a
single-owner accessor for IDs that behave like NFTs. Tools that already
understand ERC-721 ownership via ownerOf(uint256) need bespoke adapters for
these IDs today. This proposal reuses the exact ERC-721 function selector and
ERC-165 interface identifier (0x6352211e) so wallets, marketplaces,
delegation registries, indexers, and token-bound / agent-binding integrations
can resolve a single controlling account — without the contract implementing
ERC-721.
The pattern is already in production: the ENS NameWrapper exposes
ownerOf(uint256) for wrapped names (single-unit ERC-1155 IDs). This draft
generalizes the stagnant ERC-5409 to also cover ERC-6909 and pins down the
relationship between ownerOf, supply, and balances. Implementations are
informally called ERC-1155F / ERC-6909F.
interface IERC_NFMultiTokenOwnerOf {
function ownerOf(uint256 id) external view returns (address owner);
}
Key rules: every token ID has a total supply of 0 or 1; ownerOf(id) returns
the holder (who must hold exactly 1) or address(0) when unowned (before mint
or after burn) rather than reverting.
Feedback welcome!