How to Read Token Approval Limits
What unlimited and limited approvals mean and what details to verify before signing.
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When a wallet asks you to approve a token, the request usually includes a spending limit. That limit is the maximum amount the contract you are approving is allowed to move from your address, and it is the single number that determines how bad a mistake can be. “Unlimited” is not a technical necessity — it is a default chosen by the application — and understanding the difference between an unlimited approval and a capped one is the difference between a reversible annoyance and a permanent loss.
What the two figures mean
Unlimited approval. The contract is authorised to move any balance of that token you hold, at any time, now or in the future. Because balances can increase, this is effectively an open authorisation over that asset. If the approved contract contains a bug, is upgraded by its administrators, or is compromised, the reachable amount is whatever you hold at that moment. Some interfaces describe this as unlimited rather than as a very large number, so check how the value is displayed before assuming there is a cap.
Capped approval. The contract may move up to the stated amount. If it tries to move more, the transaction reverts. A cap gives you a ceiling on exposure, and the cost is that you may have to approve again once the allowance is exhausted, which is why many applications prefer the unlimited option for convenience.
Note that an approval is per token and per spender. Approving one token does not authorise another, and approving a contract does not authorise a different contract that the first one may later call.
What to verify before signing
- Check the token. Confirm the symbol and the contract address. A token with a familiar name and an unfamiliar address is a common impersonation pattern, and an approval to the wrong address grants that address control over the balance you hold of the counterfeit token.
- Check the spender. The contract requesting approval is not necessarily the application you opened. Compare the address with the official address of the protocol you intended to use.
- Check the limit value. Decide whether unlimited is acceptable for this specific contract, with this specific asset, given the amount you hold. For a token you plan to hold long term, a cap is often the more sensible choice.
- Check the chain. Approvals do not carry across networks. An approval on one chain says nothing about the same address on another.
After signing: what an approval allows
An approval is not a transfer. It does not move your tokens and it does not by itself cost you the balance. It grants a standing permission, and the risk appears later, when the approved contract calls the transfer function at any point during the lifetime of that approval.
This is why old approvals deserve attention. An approval granted to a contract that has since been abandoned, upgraded, or found to contain a bug is still in force unless it is revoked. Revoking an approval is generally a separate transaction, and revoking it does not affect the token balance — it only removes the permission.
Practical habit
Revoke approvals for applications you no longer use, particularly for anything holding unlimited amounts, and prefer exact-amount approvals when the application supports them and the expected amount is predictable. Treat an approval prompt with the same attention as a transaction, because that is what it is: a permission you are granting, not a button you are pressing.