How to remove a stuck token approval on Ethereum using MetaMask?

Understanding Token Approval Mechanics

1. Every ERC-20 token transfer on Ethereum requires prior permission via an approve call to the token contract.

2. This approval grants a specific address — often a decentralized exchange or yield protocol — the right to withdraw up to a defined amount of tokens from your wallet.

3. Approvals are immutable once confirmed on-chain; they cannot be edited, only overwritten or revoked by submitting a new transaction.

4. A 'stuck' approval typically means the allowance remains active despite no longer being needed, posing potential security exposure if the approved address is compromised.

5. The allowance value is stored in the token’s internal mapping and visible via blockchain explorers like Etherscan under the “Write Contract” tab.

Identifying the Stuck Approval

1. Open MetaMask and ensure you’re connected to the correct network — usually Ethereum Mainnet (Chain ID 1).

2. Navigate to the token’s contract page on Etherscan using its verified address.

3. Click the “Contract” tab, then scroll to “Read Contract” and expand the allowance function.

4. Enter your wallet address as the owner and the target contract address (e.g., Uniswap Router, SushiSwap MasterChef) as the spender.

5. Click “Query” — the returned value shows the remaining allowance in raw units; if non-zero, the approval is still active.

Revoking via Manual Transaction

1. Go to Etherscan’s “Write Contract” section for the same token contract.

2. Connect your wallet using the “Connect to Web3” button — MetaMask will prompt confirmation.

3. Locate the approve function and enter the spender address, then input 0 as the amount.

4. Initiate the transaction; MetaMask will display gas estimation and require signature.

5. After confirmation, wait for one block confirmation — the allowance should drop to zero, verified again via “Read Contract”.

Risks of Leaving Approvals Active

1. A malicious or compromised protocol contract could drain all approved tokens without further consent.

2. Even audited protocols may suffer logic errors that misinterpret allowance values during complex multi-step operations.

3. Phishing sites mimicking legitimate interfaces can trick users into approving arbitrary addresses with high allowances.

4. Historical incidents show attackers scanning public mempool for pending approvals and front-running them to set malicious spenders.

5. Some DeFi aggregators reuse spender addresses across versions, making old approvals unexpectedly applicable to newer deployments.

Frequently Asked Questions

Q: Can I revoke an approval without paying gas? No. Revocation requires an on-chain transaction, which consumes ETH for computation and storage update.

Q: What happens if I approve 0 to an address I previously approved with a large amount? It immediately nullifies the previous allowance. There is no grace period or delay — the change takes effect upon block inclusion.

Q: Does resetting my MetaMask account clear existing token approvals? No. Approvals exist on-chain within the token contract state, independent of wallet software or seed phrase restoration.

Q: Why does Etherscan show “Unable to verify” for some token contracts when checking allowance? That indicates the contract source code is not verified or the ABI is missing, but the allowance function remains callable if the standard ERC-20 interface is implemented.