This article was generated with AI and is republished from the BlazePhoenix blog.
An approval is standing permission for a contract to move your token — it outlives the trade, so infinite approvals are a live risk you should review and revoke.
ERC-20 tokens do not let a contract just take them — you have to grant permission first, called an approval or allowance. When you swap a token for the first time, your wallet asks you to sign two things: the approval (permission for the router to move that token) and then the swap itself. That is normal. What is easy to miss is that the approval does not expire when the trade ends — it stays live until you change it.
Many apps request an INFINITE approval by default, so you never have to approve that token again. Convenient, but it means the contract can move all of that token, forever, from your wallet. If that contract is later exploited or was malicious, your standing allowance is the door it walks through — even long after the one trade you cared about.
How to stay safe
Two habits shrink the risk. First, prefer an exact-amount approval when your wallet offers it — approve only what this trade needs, so nothing is left standing afterwards. It costs slightly more gas over time but closes the door behind you. Second, review and revoke: periodically look at what you have approved and cancel allowances you no longer use.
You can revoke from your wallet's token-approval screen or a public revoke tool; revoking is just another approval set back to zero. Treat approvals like keys you handed out — the fewer copies live in the world, the smaller your attack surface. And as always: only approve contracts you reached by typing the real URL, never from a DM or ad.
Verify it yourself: read your allowance for any token/spender with cast call "allowance(address,address)(uint256)" — a huge number is an infinite approval still live
Originally published by BlazePhoenix at https://blazephoenix.xyz/learn/token-approvals-explained. Text licensed under CC BY 4.0: credit BlazePhoenix with a link to https://blazephoenix.xyz.
Top comments (0)