Gnosis Chain: Simple soulbound token with Remix and OpenZeppelin

• Soulbound tokens are non-transferable ERC-721s, enforced via a transfer override, so they can only be minted or burned.
• This tutorial covers creating and deploying a soulbound token contract on the Gnosis Chain Chiado testnet through a Chainstack node.
• You’ll use Remix for development, MetaMask for signing, and Blockscout to verify and interact with the contract.
• Minting a token assigns it to an address, and that address alone can burn it, ensuring the token never changes ownership.

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Main article

• Create an ERC-721 contract that has a transfer override to make the token soulbound.
• Deploy the contract on the Gnosis Chain Chiado testnet through a node deployed with Chainstack.
• Interact with the deployed contract.

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Prerequisites

• Chainstack account to deploy a Gnosis Chain node.
• Remix IDE to compile the contract and deploy through MetaMask.
• MetaMask to deploy the contract through your Chainstack node and interact with the contract.

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Overview

1. With Chainstack, create a public chain project.
2. With Chainstack, join Gnosis Chain Chiado testnet.
3. With Chainstack, access your Gnosis Chain node credentials.
4. Set up your MetaMask to work through a Chainstack node.
5. With Remix IDE, create and compile the soulbound contract.
6. With Remix IDE, deploy the contract on the Gnosis Chain Chiado testnet.
7. Issue a soulbound token and burn it.

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Step-by-step

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Create a public chain project

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Join the Gnosis Chiado testnet

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Get your Gnosis Chain node access and credentials

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Set up MetaMask

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Create and compile the soulbound contract

1. Open Remix IDE.
2. On the home page, click Environments > Solidity.
3. On the left pane, click File explorers > contracts > New File.
4. In the modal, give any name to your contract. For example, soulbound.sol.
5. Put in the contract code:
   Copy

   // SPDX-License-Identifier: MIT
   pragma solidity ^0.8.7;
   
   import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
   import "@openzeppelin/contracts/utils/Counters.sol";
   import "@openzeppelin/contracts/access/Ownable.sol";
   
   contract SoulBoundToken is ERC721, Ownable {
       using Counters for Counters.Counter;
   
       Counters.Counter private _tokenIdCounter;
   
       constructor() ERC721("SoulBoundToken", "SBT") {}
   
       function safeMint(address to) public onlyOwner {
           uint256 tokenId = _tokenIdCounter.current();
           _tokenIdCounter.increment();
           _safeMint(to, tokenId);
       }
   
       function burn(uint256 tokenId) external {
           require(ownerOf(tokenId) == msg.sender, "Only the owner of the token can burn it.");
           _burn(tokenId);
       }
   
       function _beforeTokenTransfer(address from, address to, uint256) pure override internal {
           require(from == address(0) || to == address(0), "This a Soulbound token. It cannot be transferred. It can only be burned by the token owner.");
       }
   
       function _burn(uint256 tokenId) internal override(ERC721) {
           super._burn(tokenId);
       }
   }
   

   This is your soulbound token contract:
   • It uses the audited OpenZeppelin libraries to make the contract of the ERC-721 standard, belonging to the deployer, and increments each issued token ID by 1.
   • The contract has a modification to prohibit the token transfer, which makes the issued tokens soulbound.
   • The contract also implements a burn function to allow the owner of the issued token to be able to burn it.
6. Compile the contract. On the left pane, click Solidity compiler > Compile.

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Fund your account

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Set up Remix IDE to work through your Chainstack node

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Deploy the soulbound contract

1. Click Deploy & run transactions.
2. In contract, select contracts/soulbound.sol.
3. Click Deploy.

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Interact with the contract

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Flatten your contract code

1. In your Remix IDE, click Plugin manager > Flattener > Activate.
2. Click Flattener > Flatten contracts/soulbound.sol.

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Verify the deployed contract on Blockscout explorer

1. Go to Blockscout explorer.
2. Find your deployed contract. The address of your contract is on the left pane of Remix IDE under Deployed Contracts.
3. On the contract page on Blockscout, click Code > Verify & Publish.
4. Select Via flattened source code.
5. In Contract Name, provide the name of your contract. In our example, the name is SoulBoundToken.
6. In Compiler, select the same compiler version that was used in Remix IDE.
7. In Optimization, select No.
8. In Enter the Solidity Contract Code, paste the flattened contract code.
9. Click Verify & publish. Blockscout will take a few seconds to compile your contract, verify, and publish it.

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Issue a soulbound token

1. On Blockscout, on your contract, click Write Contract.
2. In your MetaMask, make sure you have the same address selected as the one that deployed the contract.
3. Click Connect wallet. This will connect your MetaMask instance with the contract owner as the active address.
4. In safeMint, provide an address that you own and to which you will issue a soulbound token.
5. Click Write.

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Burn the soulbound token

1. On Blockscout, on your contract, click Write Contract.
2. In your MetaMask, make sure you have the address selected that owns the issued soulbound token.
3. Click Connect wallet. This will connect your MetaMask instance with the token owner as the active address.
4. In burn, provide the token ID. If this is the first issued token, the ID is 0.
5. Click Write.

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Conclusion

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About the author

Ake

Director of Developer Experience @ Chainstack Talk to me all things Web320 years in technology | 8+ years in Web3 full time years experienceTrusted advisor helping developers navigate the complexities of blockchain infrastructure