I am currious of why Opensea can get all NFT contract information from blockchain? Not only does Opensea, but all the NFT marketplaces. I know that there are APIs from Etherscan or Polygonscan, but I don't find an API which returns all the contract addresses or token names. Or they just contact with Etherscan and get a private API for that fucntion? Are there any web3 experts can help with my question?
Thank you