ERC-20 Token Guide: What You Need to Know
What are ERC-20 tokens? Understand the standard behind thousands of crypto tokens, how they work, and how to use them safely.
What are ERC-20 Tokens?
ERC-20 is a technical standard for creating tokens on the Ethereum blockchain. It defines a common set of rules that all Ethereum tokens can follow, which means any ERC-20 token works with any ERC-20-compatible wallet or exchange automatically.
The standard was proposed by Fabian Vogelsteller and Vitalik Buterin in November 2015 and has since become the foundation for the vast majority of tokens on Ethereum.
There are now over 350,000 ERC-20 token contracts deployed on Ethereum.
Why ERC-20 Matters
Before ERC-20, each token had its own unique interface. This made it difficult and expensive for wallets and exchanges to support new tokens. ERC-20 standardized everything:
- Universal compatibility: Any ERC-20 token works with any Ethereum wallet (MetaMask, Ledger, Rainbow, etc.)
- Easy exchange listing: Exchanges can add support for new tokens with minimal effort
- DeFi composability: Tokens can plug into lending protocols, decentralized exchanges, and other DeFi applications seamlessly
Well-Known ERC-20 Tokens
| Token | Symbol | Purpose | Market Cap |
|---|---|---|---|
| Tether | USDT | US Dollar stablecoin | ~$140B |
| USD Coin | USDC | US Dollar stablecoin | ~$60B |
| Chainlink | LINK | Decentralized oracle network | ~$8B |
| Uniswap | UNI | DEX governance token | ~$4B |
| Aave | AAVE | Lending protocol governance | ~$2B |
Market cap figures are approximate and change constantly. Check CoinMarketCap for current numbers.
How ERC-20 Tokens Work
Every ERC-20 token contract implements the same core functions, as defined in the official standard:
- totalSupply: How many tokens exist
- balanceOf: How many tokens a specific address holds
- transfer: Send tokens from your address to another
- approve + transferFrom: Let another contract spend tokens on your behalf (used in DeFi)
Because every token follows these same rules, a single wallet app can manage thousands of different tokens without custom code for each one.
How to Store ERC-20 Tokens
Any Ethereum-compatible wallet can hold ERC-20 tokens:
- MetaMask: Most popular browser extension and mobile wallet
- Ledger: Hardware wallet for maximum security
- Rainbow: User-friendly mobile wallet
- Rabby: Security-focused browser wallet with transaction previews
Since ERC-20 tokens live on the Ethereum network, you need a small amount of ETH to pay gas fees when sending them. Without ETH in your wallet, you cannot move your tokens.
Risks
Not all ERC-20 tokens are created equal. The standard makes it easy for anyone to create a token, which means scam tokens are common.
Red flags to watch for:
- Tokens you did not buy suddenly appearing in your wallet (do not interact with them)
- Tokens with no public audit of their smart contract code
- Tokens that prevent you from selling (honeypot contracts)
- Projects with anonymous teams and no verifiable track record
Before interacting with any unfamiliar token:
- Look up the contract address on Etherscan
- Check if the contract code is verified and audited
- Search for the project on CoinGecko or CoinMarketCap to see if it is a known project
- Read the project documentation and check their GitHub for code activity
Beyond ERC-20
Ethereum has introduced other token standards for different use cases:
- ERC-721: Non-fungible tokens (NFTs), where each token is unique
- ERC-1155: Multi-token standard that can handle both fungible and non-fungible tokens in one contract
ERC-20 remains the most widely used standard and is the foundation of the DeFi ecosystem.