Revoking token approvals

Every time you trade on a DEX or deposit into a protocol, you usually approve a contract to spend a token from your wallet, often for an unlimited amount. Those permissions stay active until you change them. Revoking sends a new transaction that sets the allowance back to zero. Approval checkers in block explorers and dedicated revoke tools list every active permission per address and network and prepare the revocation for you to sign.

Old approvals are a standing risk. If a protocol you used years ago is exploited, or you once approved a malicious contract through a phishing site, the attacker can pull the approved tokens at any time without asking you again. Many drainer losses happen days after the bad approval was granted, which is why periodic clean-ups are recommended, especially for wallets that hold long-term savings.

Revoking costs a small gas fee per approval and cannot undo a theft that already happened. It also does not cover off-chain permit signatures until they are used or expire, and NFT approvals for all items in a collection need to be checked separately. Beware of fake revoke sites that are themselves drainers.