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How to deploy a smart contract to Celo testnet, Mainnet, or a local network using Remix.

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Introduction to Remix

The Remix IDE is an open-source web and desktop application for creating and deploying Smart Contracts. Originally created for Ethereum, it fosters a fast development cycle and has a rich set of plugins with intuitive GUIs. Remix is used for the entire journey of contract development and is a playground for learning and teaching Celo. In this guide, you will learn to deploy a smart contract on Celo using remix.ethereum.org.
For Celo L1 Remix does not support Solidity compiler version 0.8.20 and above for EVM versions above Paris. If you try to deploy a smart contract with a higher version, you will receive this error message:
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?

invalid opcode: opcode 0x5f not defined
The EVM version used by the selected environment is not compatible with the compiler EVM version.
A workaround is to go into the advanced settings for the compiler in Remix and choose Paris as the EVM version.For Celo Sepolia everything should be working as on every other EVM compatible chain.
To learn more about the features available to you as a smart contract developer with Remix, visit the Remix documentation.

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Create a Smart Contract

  • Navigate to remix.ethereum.org and select contracts > 1_Storage.sol from the File Explorers pane.
  • Review the smart contract code and learn more using the Solidity docs or with Solidity by Example.
  • Complete any changes to your smart contract and save the final version (Command/Ctrl + S).
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Compile the Contract

  • Choose the Solidity Compiler Icon on the left side menu.
  • Check that your compiler version is within the versions specified in the pragma solidity statement.
  • Select the Compile button to compile your smart contract.
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Deploy the Contract

  • Click the Deploy and Run Transactions Icon on the left side menu.
  • Choose Injected Web3 as your environment.
  • Connect MetaMask to Celo testnet and verify that the environment reads:
    • Custom (11142220) network for Celo Sepolia testnet
    • Custom (42220) network for Celo Mainnet
  • Click Deploy and select Confirm in the MetaMask notification window to pay for the transaction
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Interacting with the Contract

  • Select the dropdown on the newly deployed contract at the bottom of the left panel.
  • View the deployed contract’s functions using the Deployed Contracts window.
  • Select functions to read or write on the Celo testnet using the function inputs as needed.
  • Confirm write transactions in the MetaMask Notification Window to pay the transaction’s gas fee.
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View Contract Details

  • Copy the contract address from the Deployed Contracts window on the left panel.
  • Navigate to the Celo Block Explorer and use the contract address to search for your contract.
  • Explore the details of your deployed smart contract and learn more about the explorer here.
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Verify Contracts on Celo