Technical Definition

Revoke

To revoke a token approval is to remove or reduce a previously granted spending allowance for a smart contract or address.

By Crypto University Editorial
Approval / AllowanceSignatureSmart contract

✦ Key Insight

Old approvals can remain active long after a user leaves an app. Revoking unnecessary permissions reduces the amount that an approved spender could access if the spender is malicious, compromised, or no longer trusted.

✕ Common Misconceptions

Revoking one approval does not revoke every permission, signature, session key, or approval on other chains. Check the correct token contract, spender, network, and wallet before assuming access has been removed.

Detailed Explanation

Revoking usually means submitting a blockchain transaction that changes an ERC-20 allowance, commonly to zero. This stops the approved spender from using that allowance for future \`transferFrom\` calls. It does not undo transactions that already happened.

In Practice

“A user once gave a DeFi router unlimited USDT allowance. After they stop using the protocol, they set that allowance to zero so the router can no longer spend those tokens through that permission.”

Dig Deeper

Smart Contract

A smart contract is blockchain-deployed code that can hold state and execute predefined rules when called.

Wallet Address

The public string of characters others send crypto to, derived from your public key.

Approval / Allowance

An ERC-20 approval sets an allowance that lets a specified address or smart contract spend up to a defined amount of a user's tokens.

Signature

A cryptographic signature proves that the holder of a private key authorized specific data without revealing the private key itself.

Gas Fee

A gas fee is the network fee paid for computation and transaction execution on blockchains that use a gas-based fee model.