How to map and deploy custom child tokens on Polygon?

It is possible to deploy a custom child token. After you submit the form with the root token, Polygon will reach out to confirm your choice between a default child token or a custom child token mapping. Regarding extra functionality from the child token on Polygon, due to the fx_portal no longer existing, you will need to submit a mapping request to have this feature set up.

The bridge mints the Child contract via the form, and you only need to provide the Ethereum/Sepolia Parent token address. For a custom token, deploy the root token and then submit a mapping request through this portal: https://docs.polygon.technology/pos/how-to/bridging/ethereum-polygon/submit-mapping-request/. Once submitted, they will map the child token for you.

To map and deploy custom child tokens on Polygon, you need to go through a structured process that involves deploying the root token, submitting a mapping request, and coordinating with the Polygon team for proper setup. If you're looking to deploy a custom child token instead of the default one, the process includes additional steps, but it is entirely possible.

First, deploy your root token on Ethereum (or another supported Layer 1 network). This contract should follow the ERC-20, ERC-721, or ERC-1155 standard, depending on your needs. If your token requires minting functionality, make sure the contract allows it and that the appropriate supply mechanisms are in place.

Next, submit a token mapping request through Polygon’s official form, which is required for linking your root token to its Polygon counterpart. The request form is available at Polygon's Token Mapping Portal. You only need to provide the Ethereum or Sepolia parent token address. After submitting the form, Polygon will reach out to confirm whether you want a default child token or a custom child token.

If you need a custom child token, you should still start by deploying the root token and completing the mapping request. Once submitted, the Polygon team will coordinate with you to set up the child token contract. Unlike earlier systems that relied on fx_portal, the current bridge mechanism directly mints the child contract based on the mapping request. Because the bridge is responsible for minting the child token, no separate deployment is needed for standard tokens. However, if your child token requires extra functionality beyond the default setup, you'll need to communicate with Polygon's team to clarify the requirements.

The ChildChainManagerProxy address is necessary for mapping, and its value depends on the network. For reference:

• Polygon Mainnet: 0xA0c68C638235ee32657E8f720a23ceC1bFc77C77
• Amoy Testnet: 0xCf73231F28B7331BBe3124B907840A94851f9f11

These addresses are subject to change, so it's always best to verify them through Polygon’s official documentation or reach out via their Discord community.

Once your token mapping request is approved, users will be able to deposit the root token into Polygon’s PoS Bridge, and the corresponding child token will be minted on Polygon. If your child token needs special functionality, ensure you specify this when Polygon contacts you after the mapping request submission.

If the token mapping request form does not allow you to enter the child contract address, don’t worry—just submit the form with your root token details. Polygon will follow up to confirm whether you want a default or custom child token. If you're unsure about any part of the process, you can raise a support ticket through Polygon’s helpdesk or ask for guidance in Polygon Community Forum.