In order to map (to Ethereum) ERC721 Tokens that have been minted with my Smart Contract deployed on the Polygon Network:

  1. Do I need to deploy my Smart Contract on both networks (Polygon and Ethereum)?
  2. Does my Polygon Smart Contract need to have these functions: deposit() withdraw() mint()

Thank you. J

1 Answer 1


You need to deploy first on Ethereum, and then submit Token Mapping request or deploy it yourself ChildMintableERC721, this ChildMintableERC721 must be on Polygon's network based on their documentation.

To bridge to Polygon, the bridge will lock the NFTs on Ethereum and mint them on Polygon.

To bridge to Ethereum, the bridge will burn the NFT on Polygon, and unlock the original NFT on Ethereum.

  • Thank you @AdamBoudjemaa I supposed that I also have to implement the deposit() and withdraw() functions in my Smart Contract, correct? Meanwhile, I was trying to avoid deploying on Ethereum because of the gas fees. I initially thought that the RootChainManager contract would take care of the bridging for any tokens, and didn't realised that I also had to deploy a Contract on Ethereum. Just to confirm, if I do not map the contract as explained in the Polygon Documentation, users will not be able to move in any way tokens minted in my Smart Contract on Polygon to the Ethereum chain, correct?
    – JF0001
    Mar 27, 2022 at 18:37
  • 1
    I was expecting Polygon to allow users to create bridges on Ethereum, but there is no mention of that on the doc. You need to implement deposit() and withdraw() and give the right to their node to mint / burn, they will manage it. You should ask Polygon directly if you can implement the bridge on Ethereum instead of Polygon, maybe it's possible but it's not mentionned.
    – Adam Boudj
    Mar 27, 2022 at 19:03

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