Unidentified contract: OpenSea is unable to "understand" ERC-1155

Hey guys. I have deployed a ERC-1155 based contract and minted some NFTs on this contract successfully. But when I want to use these NFTs in OpenSea, it always says "Unidentified contract".

Example: https://testnets.opensea.io/assets/0xc7d3e4a5A0c3e14ba8C68ea1b8a99a9dBf3ca76F/2

API-Example: https://testnets-api.opensea.io/api/v1/asset/0xc7d3e4a5A0c3e14ba8C68ea1b8a99a9dBf3ca76F/2/?force_update=true

Following their official Tutorial repository (which does not compile any more because of outdated dependencies and other issues) I have added some (maybe) opensea-specific functions and data that might required for OpenSea in order to work properly. However, OpenSea is able to grab all required data to display an NFT, but as long as they say "Unidentified contract", this all makes no sense so far.

My question has:

has someone already managed to deploy a ERC-1155 and used it with OpenSea properly without this issue? Is there anything we have to "register" somehow contracts that are not based on ERC-721?

:1234: Code to reproduce

I have commented out some specific parts that was taken from their own tutorial which does not work without their deprecated dependencies (a very old implementation "multi-token-standard") to just keep the ABI constant in case it would matter (it does not).

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/token/ERC1155/extensions/ERC1155Burnable.sol";

import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract OwnableDelegateProxy { }

contract ProxyRegistry {
  mapping(address => OwnableDelegateProxy) public proxies;

contract MetaCoin is ERC1155, AccessControl, Pausable, ERC1155Burnable {
    bytes32 public constant URI_SETTER_ROLE = keccak256("URI_SETTER_ROLE");
    bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");

    address proxyRegistryAddress;

    uint256 private _currentTokenID = 0;
    mapping (uint256 => address) public creators;
    mapping (uint256 => uint256) public tokenSupply;

    * @dev Require msg.sender to be the creator of the token id
    modifier creatorOnly(uint256 _id) {
        require(creators[_id] == msg.sender, "ERC1155Tradable#creatorOnly: ONLY_CREATOR_ALLOWED");

    * @dev Require msg.sender to own more than 0 of the token id
    modifier ownersOnly(uint256 _id) {
        //require(balances[msg.sender][_id] > 0, "ERC1155Tradable#ownersOnly: ONLY_OWNERS_ALLOWED");

    constructor(address _proxyRegistryAddress) ERC1155("https://abcoathup.github.io/SampleERC1155/api/token/{id}.json") {       
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
        _setupRole(URI_SETTER_ROLE, msg.sender);
        _setupRole(PAUSER_ROLE, msg.sender);
        _setupRole(MINTER_ROLE, msg.sender);

        proxyRegistryAddress = /*0xF57B2c51dED3A29e6891aba85459d600256Cf317; //*/ _proxyRegistryAddress;

    function setURI(string memory newuri) public onlyRole(URI_SETTER_ROLE) {

    * @dev Returns the total quantity for a token ID
    * @param _id uint256 ID of the token to query
    * @return amount of token in existence
  function totalSupply(
    uint256 _id
  ) public view returns (uint256) {
    return tokenSupply[_id];

   * @dev Will update the base URL of token's URI
   * @param _newBaseMetadataURI New base URL of token's URI
  function setBaseMetadataURI(
    string memory _newBaseMetadataURI
  ) public /*onlyOwner*/ {

    function pause() public onlyRole(PAUSER_ROLE) {

    function unpause() public onlyRole(PAUSER_ROLE) {

    function supportsInterface(bytes4 interfaceId)
        override(ERC1155, AccessControl)
        returns (bool)
        return super.supportsInterface(interfaceId);

    function mint(address account, uint256 id, uint256 amount, bytes memory data)
        _mint(account, id, amount, data);

    function mintBatch(address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data)
        _mintBatch(to, ids, amounts, data);

    function _beforeTokenTransfer(address operator, address from, address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data)
        super._beforeTokenTransfer(operator, from, to, ids, amounts, data);

   * Override isApprovedForAll to whitelist user's OpenSea proxy accounts to enable gas-free listings.
  function isApprovedForAll(
    address _owner,
    address _operator
  ) public override view returns (bool isOperator) {
    // Whitelist OpenSea proxy contract for easy trading.
    ProxyRegistry proxyRegistry = ProxyRegistry(proxyRegistryAddress);
    if (address(proxyRegistry.proxies(_owner)) == _operator) {
      return true;

    return ERC1155.isApprovedForAll(_owner, _operator);

    * @dev Change the creator address for given token
    * @param _to   Address of the new creator
    * @param _id  Token IDs to change creator of
  function _setCreator(address _to, uint256 _id) internal creatorOnly(_id)
      creators[_id] = _to;

    * @dev Returns whether the specified token exists by checking to see if it has a creator
    * @param _id uint256 ID of the token to query the existence of
    * @return bool whether the token exists
  function _exists(
    uint256 _id
  ) internal view returns (bool) {
    return creators[_id] != address(0);

    * @dev calculates the next token ID based on value of _currentTokenID
    * @return uint256 for the next token ID
  function _getNextTokenID() private returns (uint256) {
      _currentTokenID = _currentTokenID + 1;
    return _currentTokenID;

    * @dev increments the value of _currentTokenID
  function _incrementTokenTypeId() private  {


:computer: Environment

node: v16.7.0


"@openzeppelin/contracts": "^4.3.0",
"@nomiclabs/buidler": "^1.4.8",
"@nomiclabs/hardhat-ethers": "^2.0.2",
"@nomiclabs/hardhat-etherscan": "^2.1.1",
"@nomiclabs/hardhat-waffle": "^2.0.1",
"@openzeppelin/hardhat-upgrades": "^1.9.0",
"@typechain/ethers-v5": "^6.0.5",
"@typechain/hardhat": "^1.0.1",
"@types/chai": "^4.2.15",
"@types/chai-as-promised": "^7.1.3",
"@types/mocha": "^8.2.2",
"@types/node": "^14.14.37",
"chai": "^4.3.3",
"chai-as-promised": "^7.1.1",
"chai-datetime": "^1.8.0",
"ethereum-waffle": "^3.3.0",
"ethers": "^5.4.5",
"hardhat": "^2.6.1",
"hardhat-typechain": "^0.3.5",
"ts-generator": "^0.1.1",
"ts-node": "^9.1.1",
"typechain": "^4.0.3",
"typescript": "^4.2.4"

Finally found the root cause! OpenSea expects a public property called name in order to display the proper Name on the Collection instead of "Unidentified contract".

I came across this while looking at their reference code (which depends on a now 3-year-old MultiToken-Contract implementation and needs all in all some downgrades of Node and other tools in order to get it build [a downgrade to Node 10 worked best for me today] ).