---
eip: 5409
title: EIP-1155 Non-Fungible Token extension
description: Allow EIP-1155 to represent Non-Fungible Tokens (tokens who have a unique owner)
author: Ronan Sandford (@wighawag)
discussions-to: https://ethereum-magicians.org/t/eip-5409-non-fungible-token-extension-for-eip-1155/10240
status: Stagnant
type: Standards Track
category: ERC
created: 2022-07-23
requires: 165, 721, 1155
---

## Abstract

This standard is an extension of [EIP-1155](./eip-1155.md). It proposes an additional function, `ownerOf`, which allows EIP-1155 tokens to support Non-Fungibility (unique owners). By implementing this extra function, EIP-1155 tokens can benefit from [EIP-721](./eip-721.md)'s core functionality without implementing the (less efficient) EIP-721 specification in the same contract.

## Motivation

Currently, EIP-1155 does not allow an external caller to detect whether a token is truly unique (can have only one owner) or fungible. This is because EIP-1155 do not expose a mechanism to detect whether a token will have its supply remain to be "1". Furthermore, it does not let an external caller retrieve the owner directly on-chain.

The EIP-1155 specification does mention the use of split id to represent non-fungible tokens, but this requires a pre-established convention that is not part of the standard, and is not as simple as EIP-721's `ownerOf`.

The ability to get the owner of a token enables novel use-cases, including the ability for the owner to associate data with it.

## Specification

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

### Contract Interface

```solidity
interface IERC1155OwnerOf {

    /// @notice Find the owner of an NFT
    /// @dev The zero address indicates that there is no owner: either the token does not exist or it is not an NFT (supply potentially bigger than 1)
    /// @param tokenId The identifier for an NFT
    /// @return The address of the owner of the NFT
    function ownerOf(uint256 tokenId) external view returns (address);
}
```

The `ownerOf(uint256 tokenId)` function MAY be implemented as `pure` or `view`.

The `supportsInterface` method MUST return `true` when called with `0x6352211e`.

## Rationale

`ownerOf` does not throw when a token does not exist (or does not have an owner). This simplifies the handling of such a case. Since it would be a security risk to assume all EIP-721 implementation would throw, it should not break compatibility with contract handling EIP-721 when dealing with this EIP-1155 extension.

## Backwards Compatibility

This EIP is fully backward compatible with EIP-1155.

## Security Considerations

Needs discussion.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).