ERC-20 Token Standard

⬢ TIER 1Tech

High

Salary impact

1 months

Time to learn

Medium

Difficulty

—

Careers

At a glance

ERC-20 is the Ethereum standard for fungible tokens (identical, interchangeable). Think of them like dollars, one unit equals another. ERC-20 contracts define balances, transfers, and approvals. Every major token (USDC, DAI, LINK) is ERC-20. Learning takes 1-2 weeks for Solidity devs; mastery (minting, burning, access control, security) takes 2-3 months. Senior token engineers earn $150K+ because poorly-designed tokens leak millions to hacks.

What is ERC-20 Token Standard

ERC-20 is Ethereum's standard for fungible tokens, digital assets where each unit is identical and interchangeable. Think of them like dollars: one $1 bill equals another $1 bill. ERC-20 contracts implement a standard interface: balanceOf (check balance), transfer (send tokens), approve (allow someone else to spend), and transferFrom (spend approved tokens). Exchanges, wallets, and DeFi protocols understand ERC-20 because the interface is standardized. Deploy an ERC-20 contract and it automatically works on OpenSea, Uniswap, MetaMask, no integration needed.

🔧 TOOLS & ECOSYSTEM

SolidityOpenZeppelin contractsHardhat or TruffleWeb3.js or Ethers.jsMetaMaskRemix IDE

💰 Salary by region

Region	Junior	Mid	Senior
USA	$90k	$150k	$230k
UK	$55k	$92k	$140k
EU	$60k	$100k	$150k
CANADA	$95k	$160k	$250k

🎓 Certifications

ERC-20 Specification OpenZeppelin ERC-20 Implementation Solidity by Example, ERC-20

❓ FAQ

What's the difference between transfer() and transferFrom()?

transfer: I send tokens directly from my wallet to someone else. transferFrom: Someone already approved me to spend X tokens, and I move them. Approve first, then transferFrom. Like pre-authorizing a merchant to charge your card.

Why do I need approve() before transferFrom()?

Security. If transfer was automatic, approving a contract to swap tokens would give it unlimited access to your wallet. Approve limits the contract's spending to a specific amount. Revoke approval when done.

What happens if total supply is unlimited?

Token value approaches zero due to inflation. Most tokens cap total supply. Some (like Ethereum's ETH) don't have a hard cap, but have emission schedules. Set totalSupply to a number and enforce it.

How do I implement taxes or fees on transfers?

Override transfer() and transferFrom(). Calculate 2% fee, send to treasury, transfer remaining 98% to recipient. But this breaks expected behavior, users send 100 tokens, receive 98. Consider this UX impact.

Can I make tokens non-transferable?

Yes. Override transfer and revert if !isOwner. Used for vesting tokens (employees can't sell for X years). Or use pausable pattern: owner can pause transfers globally.

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