Token approval (allowance)

A token approval, or allowance, is permission you give a smart contract to move a particular token from your wallet. On Ethereum and other EVM chains, before a DEX can swap your USDT or a marketplace can sell your NFT, you must sign an approval transaction allowing its contract to spend that token.

Many apps request an "unlimited" approval so you do not need to approve again for every trade. That is convenient but risky: if the contract is malicious or later hacked, it can drain all of that token from your wallet at any time, without asking again. Wallet drainers often trick users into signing approvals or "permit" signatures that look harmless.

To stay safe, read what your wallet asks you to sign, set approval amounts to what you actually need where possible, and periodically review and revoke old approvals using tools such as Revoke.cash or Etherscan's token approval checker. Revoking costs a small gas fee but closes the door.