When an approval is still active
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 6 min
In short
Using decentralised apps can leave contracts holding permission to move your tokens. That permission stays valid even at a zero balance, so it can drain tokens the moment you deposit them later. Review your approvals with a checking tool and revoke the ones you no longer use — bearing in mind that revoking itself costs a network fee.
Key points
- Approvals persist per token and per contract, and nothing expires them automatically
- An unlimited approval covers your entire balance of that token
- Revoking is an on-chain action and therefore costs a network fee
- Reach any checking tool through official sources — fake 'revoke' sites exist
Definition
A still-valid permission granted to a contract allowing it to move your tokens. The allowance has a cap, which is sometimes set to unlimited.
Understand the mechanism first. For most tokens, a contract such as a decentralised exchange needs your permission before it can move them, and that permission is the approval. Approvals carry a cap, which is often set to unlimited for convenience. And once granted, an approval remains valid until you explicitly revoke it — it does not lapse when the trade ends or when you stop using the app.
The danger arrives later. If a flaw is found in the approved contract, or whoever runs it turns malicious, that permission can be used to move your balance. A zero balance at the time is irrelevant: deposit the same token later and it is exposed again, up to the cap. Losses to old approvals are reported continuously.
Here is the process. Use a tool that lists the approvals granted from your address. The critical part is how you reach that tool: not from the top of search results, and not from a link shared on social media. Fake sites advertising 'bulk approval revocation' exist, and connecting and signing there is exactly how wallets get emptied. Reach the tool through your wallet's or an explorer's official documentation.
Once you have the list, revoke in priority order: unlimited allowances first, then contracts you do not recognise, then apps you used only once. Each revocation is its own on-chain transaction with its own fee, so clearing everything at once gets expensive. Working down from the riskiest across a few sessions is the practical approach; 'How to revoke a token approval' has the steps.
As an ongoing habit, schedule a periodic review. Splitting your holdings between a wallet you use day to day and one that simply holds long-term assets also shrinks how much any approval can reach — 'Separating your wallets' explains the reasoning.
Watch out for
- · Do not connect to sites advertising bulk revocation. Fakes exist that request a fresh approval while posing as a revoke
- · Revoking costs fees. For a wallet with little in it, moving the assets to another wallet is sometimes the more sensible answer
- · Revoking does not return anything already taken. Review approvals before there is a loss, not after
Frequently asked questions
Should I revoke on a wallet with a zero balance?
If you intend to keep using that wallet, yes. Approvals are valid regardless of balance, so they apply again the moment you deposit. If you have decided never to use it again, leaving it and moving to a new wallet is also a defensible choice.