VEYRNOX · Learn · ERC-20 Token
ERC-20 Token
ERC-20 is the Ethereum standard for fungible tokens. It defines a common interface — balanceOf, transfer, approve, transferFrom — that every wallet, exchange, and dApp can rely on. USDC, USDT, DAI, LINK, UNI, and thousands of other tokens are ERC-20s.
How it works
An ERC-20 token is a smart contract that maintains a ledger mapping addresses to balances. Transferring the token calls the contract’s transfer function, which debits the sender and credits the receiver. Approvals — the approve and transferFrom pair — let contracts move tokens on the user’s behalf, up to a set allowance. Unlike native ETH transfers, ERC-20 transfers require the recipient to interact with the token contract to see the balance, which is why wallets need per-token discovery.
Why it matters
ERC-20 is the interoperability layer that made DeFi possible. Every DEX, lending market, and yield vault speaks ERC-20; new tokens integrate with the entire ecosystem for free. The trade-off is the approval pattern, which is the attack surface behind most drainer contracts. Wallet transaction simulation exists largely to make approvals safe.
Related concepts
- WalletConnect v2 — WalletConnect v2 is an open protocol that lets a wallet on one device connect to a dApp on another — most commonly a mobile wallet paired with a desktop dApp — over an end-to-end-encrypted relay.
- Transaction Simulation — Transaction simulation is a pre-signing check that runs a proposed transaction against a forked node state and reports the expected net asset change to the user before they sign.
- Drainer Contract — A drainer contract is a malicious smart contract that, once approved by a victim, transfers assets out of the victim’s wallet to attacker-controlled addresses.
- dApp — A dApp — decentralized application — is a frontend that interacts with smart contracts on a public blockchain.
Frequently asked questions
What is an unlimited approval?
An approval for the maximum uint256 value, which lets the contract move any amount at any time. Convenient for DeFi, catastrophic for drainers.
Can I revoke an ERC-20 approval?
Yes — set the allowance back to zero. Tools like revoke.cash let you audit and remove existing approvals.
Are ERC-20 tokens their own coins?
They live on Ethereum (or an EVM chain). Sending ETH is a native transfer; sending USDC is a contract call.
In Veyrnox
Veyrnox supports ERC-20 tokens including USDC, USDT, DAI, and LINK. Approvals are surfaced with transaction simulation output so the user sees exactly what they are granting.