NFT Knowledge 2 — Questions and Answers
Question 1: Which Ethereum standard is most commonly used to implement non-fungible tokens?
- ERC-20
- ERC-721 (Correct answer)
- ERC-1155
- ERC-777
Correct answer: ERC-721
ERC-721 is the canonical standard defining unique, non-fungible tokens on Ethereum.
Question 2: What does the tokenURI function in an ERC-721 contract typically return?
- The owner's wallet address
- A pointer to the token's metadata (often JSON) (Correct answer)
- The current sale price
- The contract's bytecode
Correct answer: A pointer to the token's metadata (often JSON)
tokenURI returns a URI pointing to a metadata document describing the NFT.
Question 3: Why are NFT images and metadata often stored on IPFS rather than directly on-chain?
- IPFS is faster than any database
- On-chain storage of large files is prohibitively expensive in gas (Correct answer)
- IPFS encrypts all data automatically
- Ethereum bans storing images
Correct answer: On-chain storage of large files is prohibitively expensive in gas
Storing large media on-chain costs enormous gas, so decentralized off-chain storage like IPFS is used.
Question 4: In ERC-721, which function transfers ownership while checking the recipient can handle NFTs?
- transfer()
- safeTransferFrom() (Correct answer)
- send()
- mint()
Correct answer: safeTransferFrom()
safeTransferFrom verifies that a contract recipient implements onERC721Received before transferring.
Question 5: What is 'minting' an NFT?
- Burning a token permanently
- Creating a new token and recording it on-chain (Correct answer)
- Selling a token on a marketplace
- Approving a transfer
Correct answer: Creating a new token and recording it on-chain
Minting is the process of generating a new token and writing it to the blockchain.
Question 6: Which event must an ERC-721 contract emit when a token changes owner?
- Approval
- Transfer (Correct answer)
- Mint
- OwnershipMoved
Correct answer: Transfer
The Transfer event signals ownership changes including mints and burns.
Question 7: What advantage does ERC-1155 offer over ERC-721?
- It only supports fungible tokens
- It can manage multiple token types (fungible and non-fungible) in one contract (Correct answer)
- It eliminates the need for gas
- It is incompatible with NFTs
Correct answer: It can manage multiple token types (fungible and non-fungible) in one contract
ERC-1155 is a multi-token standard supporting batch operations and mixed token types in a single contract.
NFT Knowledge 2
Which Ethereum standard is most commonly used to implement non-fungible tokens?