Is there a specific EIP that allows for collections of NFTs to be created or are NFT collections completely off-chain? If there is a way to create an NFT collection (group of NFTs) on chain, how?

Also, if you see an NFT collection in a marketplace, is each NFT made with individual contract or the same contract? If it is the same contract could you show me an example?

If I was minting NFTs with solidity instead of a site such as opensea, how can I make it show up on OpenSea as a collection if possible?

Thank you!

1 Answer 1


NFTs are smart contracts that follow the ERC721 standard.

NFT smart contracts are fully on chain, however they may or may not point to an off-chain URI.

The URI is the variable that points to the NFT metadata. It often points towards an IPFS cloud but could also be any server. It is also possible to store your NFT as a SVG file. There are many guides on this.

Marketplaces like Opensea will automatically detect any deployed ERC721 contract and show any minted item of a collection. Each "unique NFT" is infact only a minted token from one NFT smart contract. As soon as a different contract is used, it is effectively a different collection. If tokenId 1 is minted and tokenId 2 is minted, the collection has 2 NFTs.

Highly recommend watching youtube video to understand the concept. For example, here is one that explains the contract side.

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