NFT Guide 3

Question 1

Which interface detection standard lets contracts advertise that they support ERC-721?

Accepted Answer

ERC-165

Answer

ERC-165 provides supportsInterface, which contracts use to declare ERC-721 compliance.

Question 2

What is a common reason to use a Merkle tree in an NFT mint contract?

Accepted Answer

To gate an allowlist efficiently on-chain

Answer

A Merkle root lets the contract verify allowlist membership without storing every address.

Question 3

Why is using block.timestamp or blockhash for NFT trait randomness considered insecure?

Accepted Answer

Miners or validators can influence or predict it

Answer

On-chain values like blockhash are predictable or manipulable, so a service like Chainlink VRF is preferred.

Question 4

What does 'lazy minting' refer to in NFT development?

Accepted Answer

Deferring the on-chain mint and gas cost until the first sale

Answer

Lazy minting creates the token on-chain only when it is purchased, shifting gas costs to the buyer.

Question 5

In the ERC-721 metadata JSON, which field conventionally holds the displayed picture link?

Accepted Answer

image

Answer

The metadata standard uses an 'image' field containing a URL to the asset.

NFT Development Practice Test