How dApp developers can use MetaMask to interact with the Celo network.

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Adding a Celo Network to MetaMask

To add a Celo Network to your dApp, you can use MetaMask’s RPC API’s wallet_addEthereumChain method. (See documentation). Here is a JavaScript snippet you can use: 
await window.ethereum.request({
    method: 'wallet_addEthereumChain',
    params: [<INSERT_NETWORK_PARAMS_HERE>],
});
Where it says INSERT_NETWORK_PARAMS_HERE, please replace with any of the following constants, depending on which network you’d like to connect to.

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Mainnet

const CELO_PARAMS = {
  chainId: "0xa4ec",
  chainName: "Celo",
  nativeCurrency: { name: "Celo", symbol: "CELO", decimals: 18 },
  rpcUrls: ["https://forno.celo.org"],
  blockExplorerUrls: ["https://celo.blockscout.com/"],
  iconUrls: ["future"],
};

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Celo Sepolia

const CELO_SEPOLIA_PARAMS = {
  chainId: "0xAA044C",
  chainName: "Celo Sepolia",
  nativeCurrency: { name: "Celo", symbol: "S-CELO", decimals: 18 },
  rpcUrls: ["https://forno.celo-sepolia.celo-testnet.org/"],
  blockExplorerUrls: ["https://celo-sepolia.blockscout.com/"],
  iconUrls: ["future"],
};

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Alfajores (deprecated)

const ALFAJORES_PARAMS = {
  chainId: "0xaef3",
  chainName: "Alfajores Testnet",
  nativeCurrency: { name: "Alfajores Celo", symbol: "S-CELO", decimals: 18 },
  rpcUrls: ["https://alfajores-forno.celo-testnet.org"],
  blockExplorerUrls: ["https://celo-alfajores.blockscout.com/"],
  iconUrls: ["future"],
};

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Adding Tokens (e.g. cUSD, cEUR)

To watch an asset on a Celo network (e.g. cUSD, cEUR) in your dApp, you can use MetaMask’s RPC API’s wallet_watchAsset method. (See documentation). Here is a JavaScript snippet you can use: 
await window.ethereum.request({
  method: "wallet_watchAsset",
  params: {
    type: "ERC20",
    options: {
      address: "<INSERT_ADDRESS_HERE>",
      symbol: "<INSERT_SYMBOL_HERE>",
      decimals: 18,
    },
    iconUrls: ["future"],
  },
});
  • Where it says INSERT_ADDRESS_HERE, please replace with any of the following constants, depending on which network and which asset you’d like to connect to.
  • Where it says INSERT_SYMBOL_HERE, please replace with the correct symbol for the asset you’d like to watch. For Celo Dollars, it’s cUSD and for Celo Euros, it’s cEUR.
View available token addresses for Celo assets to add to MetaMask here.
We strongly suggest that you disable your dApp’s functionality when MetaMask is connected to a non-Celo network. MetaMask has an API for determining what network/chain you’re connected to. See here for more documentation around that.