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  • NFT Smart Contract Interview Question: ERC-721 & ERC-1155 Compatibility

    amanda smith

    Member

    Updated: Apr 30, 2025
    Views: 1.1K

    How do you design a single NFT contract that handles both ERC-721 and ERC-1155 standards without gas fees going nuts?

    I bombed this interview question for a blockchain dev role and need to figure this out.

    Here’s the deal: ERC-721 is for unique stuff like digital art, ERC-1155 does batches for games-but how do you merge them into one contract that actually works on platforms like OpenSea?

    And how do you keep gas fees low when minting single NFTs vs. batches in the same contract?

    Are there OpenZeppelin shortcuts or design patterns that make this less of a headache? Bonus points if you’ve got code snippets or interview-ready explanations.

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  • Lilly Gomes

    Member • 6mos

    To build an NFT contract that supports both ERC-721 and ERC-1155 standards, focus on a clear, modular structure and efficient gas usage to achieve compatibility across platforms and marketplaces.

    1. Use Solidity Inheritance: Structure your contract by inheriting from both ERC-721 and ERC-1155 standards. OpenZeppelin libraries can provide reliable base contracts for this, allowing you to handle single and batch minting in one contract. ERC-721 is ideal for single unique NFTs, while ERC-1155’s batch functionality supports multiple tokens in a single transaction.

    2. Separate Minting Functions: Define distinct functions for each type of minting. For example, use a mint function for single NFT (ERC-721) minting and mintBatch for ERC-1155 batch minting. This division keeps the logic clear and reduces gas costs by limiting unnecessary computations within each function.

    3. Optimize Gas Usage: Reduce gas fees by minimizing storage updates and reusing storage variables where possible. Use ERC-1155’s batch minting where applicable, as it can handle multiple items more efficiently. Offload metadata to an off-chain source when feasible, with only a reference stored on-chain to cut down on storage costs.

    4. Ensure Compatibility with Marketplaces: Implement interfaces like IERC721, IERC1155, and IERC165. These interfaces help marketplaces recognize the standards, allowing smooth listing and trading. Compatibility checks are key to making your contract widely accessible.

    5. Test Thoroughly: Use tools like Hardhat and Truffle to run comprehensive tests on single and batch minting functions. Test on various wallets and platforms to confirm your contract’s compatibility and performance under different conditions.

    This method will allow your NFT contract to handle both single and batch minting efficiently, supporting widespread usage and marketplace compatibility.

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