i have a question and i think someone can help me.

I'm developing an NFT Marketplace, and i already have the Smart contract, but i don't know how Marketplaces like OpenSea or Rarible have ALL the nfts existing in the Ethereum, polygon and solana Networks. I want to know how to do that, so i can show the nfts also in my marketplace.

Hope somebody can help me.

1 Answer 1


In order to know what tokens an address owns, the only way is to keep track of all transactions of an address and keeping track of records. However, there are 3rd party services that provides that information for you and using their API you can query what NFTs are on your wallet.

Covalent offers a free API for querying the token balances of an address, including NFTs. Documentation is here.

  • And if i want to track all nfts erc721 and 1155 existing in the mainnet and show them in my frontend, like the collections page of opensea, how do i do that?
    – john gomez
    Jul 3, 2022 at 18:09

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