ERC-20 Token Standard Explained | Build Your Own Token in Solidity (Full Tutorial)

In this tutorial, you'll learn everything about the ERC-20 token standard — the backbone of DeFi, ICOs, stablecoins, and governance tokens on Ethereum. We break down the full IERC20 interface, implement a working ERC-20 contract from scratch in Solidity, and explain the powerful approve() + transferFrom() two-step pattern that powers protocols like Uniswap. What you'll learn: What ERC-20 is and why it matters The 6 required functions and 2 events every ERC-20 token must have How totalSupply, balanceOf, transfer, approve, allowance, and transferFrom work How DeFi protocols access your tokens safely using approve + transferFrom How to implement internal _mint() and _burn() functions Full Solidity implementation using Solidity v0.8.35 Perfect for Solidity beginners and developers looking to understand how tokens like USDC, DAI, and UNI actually work under the hood. Source: solidity-by-example.org/app/erc20 Chapters: 00:00 Introduction - Token Standars I - ERC20 00:25 ICOs - Short Description 00:42 Ethereum Request for Comments - 20 01:40 Answering - When can we call a token contract to be ERC-20 compatible? 06:40 ERC20 code implementation: IERC20 07:20 Key Takeaway - approve() + transferFrom() - two step pattern 08:08 ERC20 is IERC20, State Variables, Mappings & Constructor 09:35 function transfer(address to, uint256 amount) external returns (bool) 11:15 Overflow/Underflow in balance update 12:18 function approve(address spender, uint256 amount) external returns (bool) 13:26 function transferFrom(address from, address to, uint256 amount) external returns (bool) 14:40 Internal functions _mint() & _burn() 15:30 Gotcha: Transfer event - address(0) parameter 16:30 function _burn(address from, uint256 amount) internal 17:00 Summary & Key Takeaways 18:50 IMPORTANT: Rectifying Typo In PPT 19:15 Thank You #solidity #erc20 #ethereum #smartcontracts #blockchaindevelopment #defi #web3 #learnsolidity #cryptotokens #soliditytutorial