EIPs/EIPS/eip-1155.md

---
eip: 1155
title: Multi Token Standard
author: Witek Radomski <witek@enjin.com>, Andrew Cooke <andrew@enjin.com>
type: Standards Track
category: ERC
status: Draft
created: 2018-06-17
discussions-to: https://github.com/ethereum/EIPs/issues/1155
---

## Simple Summary

A standard interface for contracts that manage multiple token types. A single deployed contract may include any combination of fungible tokens, non-fungible tokens, or other configurations (for example, semi-fungible tokens).

## Abstract

This standard outlines a smart contract interface where one can represent any number of Fungible and Non-Fungible assets in a single contract. Existing standards such as ERC-20 require deployment of separate contracts per token. The ERC-721 standard's Token ID is a single non-fungible index and the group of these non-fungibles is deployed as a single contract with settings for the entire collection. Instead, the ERC-1155 Multi Token Standard allows for each Token ID to represent a new configurable token type, which may have its own totalSupply value and other such attributes.

The `_id` parameter is contained in each function's parameters and indicates a specific token or token type in a transaction.

## Motivation

Tokens standards like ERC-20 and ERC-721 require a separate contract to be deployed for each fungible or NFT token/collection. This places a lot of redundant bytecode on the Ethereum blockchain and limits certain functionality by the nature of separating each token contract into its own permissioned address. With the rise of crypto games and platforms like [Enjin Coin](https://enjincoin.io/), game developers may be creating thousands of tokens, and a new type of token standard is needed to support this.

New functionality is possible with this design, such as transferring or approving multiple token types at once, saving on transaction costs. Trading (escrow / atomic swaps) of multiple tokens can be built on top of this standard and it removes the need to "approve" individual tokens separately. It is also easy to describe and mix multiple fungible or non-fungible tokens in a single contract.

### Batch Transfers

The `safeBatchTransferFrom` function allows for batch transfers of multiple token ids and values. Gas savings improves with the number of token types in the batch transfer, compared to single transfers with multiple transactions.

### Backwards Compatibility

This standard is compatible with ERC-721 non-fungible tokens. Both interfaces can be inherited without conflict:

```solidity
contract MultiTokens is ERC1155, ERC721 {
    ...
}
```

# Specification

```solidity
pragma solidity ^0.4.24;

/**
    @title ERC-1155 Multi Token Standard
    @dev Note: the ERC-165 identifier for this interface is 0xf23a6e61.
 */
interface ERC1155 {
    /**
        @dev MUST emit when tokens are transferred, including zero value transfers
    */
    event Transfer(address _spender, address indexed _from, address indexed _to, uint256 indexed _id, uint256 _value);

    /**
        @dev MUST emit on any successful call to approve(address _spender, uint256 _id, uint256 _currentValue, uint256 _value)
    */
    event Approval(address indexed _owner, address indexed _spender, uint256 indexed _id, uint256 _oldValue, uint256 _value);
    
    /**
        @dev MUST emit on any successful call to setApprovalForAll(address _operator, bool _approved)
    */
    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
    
    /**
        @dev Emits when the URI is updated for a token ID
    */
    event URI(uint256 indexed _id, string _value);
    
    /**
        @dev Emits when the Name is updated for a token ID
    */
    event Name(uint256 indexed _id, string _value);
    
    /**
        @notice Transfers value amount of an _id from the _from address to the _to addresses specified. Each parameter array should be the same length, with each index correlating.
        @dev MUST emit Transfer event on success.
        Caller must have sufficient allowance by _from for the _id/_value pair, or isApprovedForAll must be true.
        Throws if `_to` is the zero address.
        Throws if `_id` is not a valid token ID.
        When transfer is complete, this function checks if `_to` is a smart contract (code size > 0). If so, it calls `onERC1155Received` on `_to` and throws if the return value is not `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`.
        @param _from    source addresses
        @param _to      target addresses
        @param _id      ID of the Token
        @param _value   transfer amounts
        @param _data    Additional data with no specified format, sent in call to `_to`
    */
    function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes _data) external;
    
    /**
        @notice Send multiple types of Tokens from a 3rd party in one transfer (with safety call)
        @dev MUST emit Transfer event per id on success.
        Caller must have a sufficient allowance by _from for each of the id/value pairs.
        Throws on any error rather than return a false flag to minimize user errors.
        @param _from    Source address
        @param _to      Target address
        @param _ids     Types of Tokens
        @param _values  Transfer amounts per token type
        @param _data    Additional data with no specified format, sent in call to `_to`
    */
    function safeBatchTransferFrom(address _from, address _to, uint256[] _ids, uint256[] _values, bytes _data) external;
    
    /**
        @notice Allow other accounts/contracts to spend tokens on behalf of msg.sender
        @dev MUST emit Approval event on success.
        To minimize the risk of the approve/transferFrom attack vector (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), this function will throw if the current approved allowance does not equal the expected _currentValue, unless _value is 0.
        @param _spender      Address to approve
        @param _id           ID of the Token
        @param _currentValue Expected current value of approved allowance.
        @param _value        Allowance amount
    */
    function approve(address _spender, uint256 _id, uint256 _currentValue, uint256 _value) external;
    
    /**
        @notice Get the balance of an account's Tokens
        @param _id     ID of the Token
        @param _owner  The address of the token holder
        @return        The _owner's balance of the Token type requested
     */
    function balanceOf(uint256 _id, address _owner) external view returns (uint256);
    
    /**
        @notice Queries the spending limit approved for an account
        @param _id       ID of the Token
        @param _owner    The owner allowing the spending
        @param _spender  The address allowed to spend.
        @return          The _spender's allowed spending balance of the Token requested
     */
    function allowance(uint256 _id, address _owner, address _spender) external view returns (uint256);
    
    /**
        @notice Enable or disable approval for a third party ("operator") to manage all of `msg.sender`'s assets.
        @dev MUST emit the ApprovalForAll event on success.
        @param _operator  Address to add to the set of authorized operators
        @param _approved  True if the operator is approved, false to revoke approval
    */
    function setApprovalForAll(address _operator, bool _approved) external;
    
    /** 
        @notice Queries the approval status of an operator for a given Token and owner
        @param _owner     The owner of the Tokens
        @param _operator  Address of authorized operator
        @return           True if the operator is approved, false if not
    */
    function isApprovedForAll(address _owner, address _operator) external view returns (bool isOperator);
}
```
</details>

The following optional extensions can be identified with the (ERC-165 Standard Interface Detection)[https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md].

<details>
<summary>
Multicast Transfers</summary>

### Multicast Transfers

The `ERC1155Multicast` extension allows for multicast transfers to and from multiple addresses. It's also possible to create a simple atomic swap using this function by first obtaining approvals from the source and destination parties.

```solidity
interface ERC1155Multicast {
    /**
        @dev Send multiple types of Tokens in one transfer from multiple sources.
        @param _from    Source addresses
        @param _to      Transfer destination addresses
        @param _ids     Types of Tokens
        @param _values  Transfer amounts
    */
    function multicastTransferFrom(address[] _from, address[] _to, uint256[] _ids, uint256[] _values) external;
}
```

</details>

<details>
<summary>
Token ID Approval</summary>

```solidity
interface ERC1155Operators {
    event OperatorApproval(address indexed _owner, address indexed _operator, uint256 indexed _id, bool _approved);

    /**
        @notice Enable or disable approval for a third party ("operator") to manage
        all of `msg.sender`'s assets for a particular Token types.
        @dev Emits the OperatorApproval event
        @param _operator  Address to add to the set of authorized operators
        @param _ids       The IDs of the Tokens
        @param _approved  True if the operators is approved, false to revoke approval
    */
    function setApproval(address _operator, uint256[] _ids, bool _approved) external;
    
    /**
        @notice Queries the approval status of an operator for a given Token and owner
        @param _owner     The owner of the Tokens
        @param _operator  Address of authorized operator
        @param _id        ID of the Token
        @return           True if the operator is approved, false if not
    */
    function isApproved(address _owner, address _operator, uint256 _id)  external view returns (bool);
}
```

</details>

<details>
<summary>
Metadata / Views</summary>

```solidity
interface ERC1155MetadataURI {
    /**
        @notice A distinct Uniform Resource Identifier (URI) for a given asset
        @dev URIs are defined in RFC 3986
        @return  URI string
    */
    function uri(uint256 _id) external view returns (string);
}

interface ERC1155MetadataName {
    /**
        @notice Returns a human readable string that identifies a Token, similar to ERC20
        @param _id  ID of the Token
        @return     The name of the Token type
     */
    function name(uint256 _id) external view returns (string);
}
```

</details>

## ERC-1155 Token Receiver

Smart contracts **MUST** implement this interface to accept safe transfers.

```solidity
interface ERC1155TokenReceiver {
    /**
        @notice Handle the receipt of an ERC1155 type
        @dev The smart contract calls this function on the recipient
        after a `safeTransferFrom`. This function MAY throw to revert and reject the
        transfer. Return of other than the magic value MUST result in the
        transaction being reverted
        Note: the contract address is always the message sender
        @param _operator  The address which called `safeTransferFrom` function
        @param _from      The address which previously owned the token
        @param _id        The identifier of the token being transferred
        @param _value     The amount of the token being transferred
        @param _data      Additional data with no specified format
        @return           `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
    */
    function onERC1155Received(address _operator, address _from, uint256 _id, uint256 _value, bytes _data) external returns(bytes4);
}
```

<details>
<summary>
Non-Fungible Tokens</summary>

### Discussion

An example strategy to mix Fungible and Non-Fungible tokens together in the same contract would be to pass the base token ID in the top 128 bits of the uint256 `_id` parameter and then use the bottom 128 bits for any extra data you wish to pass to the contract.

Non-Fungible tokens can be interacted with using an index based accessor into the contract/token data set. Therefore to access a particular token set within a mixed data contract and particular NFT within that set, `_id` could be passed as `<uint128: base token id><uint128: index of NFT>`.

Inside the contract code the two pieces of data needed to access the individual NFT can be extracted with uint128(~0) and the same mask shifted by 128.

### Interface

```solidity
interface ERC1155NonFungible {
    /**
        @notice Find the owner of an NFT
        @dev NFTs assigned to zero address are considered invalid, and queries about them do throw
        @param _id  The identifier for an NFT
        @return     The address of the owner of the NFT
    */
    function ownerOf(uint256 _id) external view returns (address);
    
    /**
        @notice Enumerate valid NFs
        @dev Throws if `_index` >= `totalSupply()`.
        @param _index  A counter less than `totalSupply()`
        @return        The token identifier for the `_index`th NFT (sort order not specified)
    */
    function nonFungibleByIndex(uint256 _id, uint128 _index) external view returns (uint256);
    
    /**
        @notice Enumerate NFTs assigned to an owner
        @dev Throws if `_index` >= `balanceOf(_owner)` or if
        `_owner` is the zero address, representing invalid NFTs
        @param _owner  An address where we are interested in NFTs owned by them
        @param _index  A counter less than `balanceOf(_owner)`
        @return        The token identifier for the `_index`th NFT assigned to `_owner` (sort order not specified)
    */
    function nonFungibleOfOwnerByIndex(uint256 _id, address _owner, uint128 _index) external view returns (uint256);
    
    /**
        @notice Is this token non fungible?
        @dev If this returns true, the token is non-fungible.
        @param _id  The identifier for a potential non-fungible.
        @return     True if the token is non-fungible
    */
    function isNonFungible(uint256 _id) external view returns (bool);
}
```

### Example of split ID bits

```solidity
uint256 baseToken = 12345 << 128;
uint128 index = 50;

balanceOf(baseToken, msg.sender); // Get balance of the base token
balanceOf(baseToken + index, msg.sender); // Get balance of the Non-Fungible token index
```

</details>

## Implementation

- [ERC-1155 Reference Implementation](https://github.com/enjin/erc-1155)
- [Enjin Coin](https://enjincoin.io) ([github](https://github.com/enjin))

## Copyright
Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).