If you’re moving an ERC-20 token across a bridge, an EIP-2612 permit can let you sign an allowance instead of sending a separate approval transaction. It authorizes a specific spender to use a set amount of one token on one chain; the bridge still needs a transaction to take the tokens and start the transfer.
A permit signs an allowance for one token and spender
An ERC-20 allowance lets a contract spend tokens from your wallet through transferFrom. Usually, you first send an on-chain approve transaction to the token contract. EIP-2612 lets you sign typed data authorizing that allowance, so a compatible contract can submit the permit on-chain as part of a later transaction.
The signature names the token owner, spender, allowance value, nonce and deadline. It is tied to the token contract and chain through its EIP-712 domain. The spender should be the contract that will pull the tokens for the bridge transaction; the permit itself does not tell a bridge where to send assets or move them between networks.
That distinction matters when using Mantle Bridge: a permit, if the token and route support it, relates to the token on the source chain. Bridging still requires a separate transfer operation. For the broader process of moving funds for a treasury, see how Mantle Bridge handles treasury transfers; this article focuses on what the signed approval does.
The bridge must consume the permit before pulling tokens
A permit is just a signed message until a transaction submits it to the token contract. In a combined flow, a bridge contract or router calls permit, which records the allowance, then calls transferFrom to take the approved tokens. If both calls happen in one transaction, the approval and token pull can succeed together or revert together.
Some applications instead submit the permit in its own transaction, then start the bridge transfer. That creates a real on-chain allowance between the two transactions. A bridge may also use ordinary approve if its route does not support permit consumption. Signing a permit does not mean the application will use one; the wallet prompt and transaction flow determine what is actually being requested.
For example, assume you want to bridge 1.5 USDC from Ethereum and the exact USDC contract and bridge route support EIP-2612. With USDC’s six decimal places, a permit for exactly that amount uses a value of 1,500,000 base units. The bridge spender can then pull up to that amount from the Ethereum token contract. This is an illustrative amount; check the token’s decimals and the amount shown in the actual signing request.
Check the signature fields before signing
For a bridge approval, confirm that the typed-data request matches the action you intend to authorize. The owner should be your wallet, the spender should be the expected bridge contract or router, and the value should cover only the intended amount unless you deliberately choose a larger allowance. The deadline limits how long the signature can be submitted; a short window reduces the time an unused signature remains valid.
The permit’s nonce prevents replay: after a valid permit is used, the token increments that owner’s nonce, so the same signature cannot be reused. Its chain and token domain also bind it to a particular token contract on a particular chain. An Ethereum permit does not approve a different token contract on Mantle, even when both tokens have the same ticker or represent the same asset.
One easy mistake is to assume a ticker guarantees permit support. EIP-2612 is an optional token feature, and implementations can differ; a token called USDT, USDC or MNT on one chain may not expose the same permit function as a token with that name elsewhere. Native ETH is not an ERC-20 token and has no ERC-2612 allowance, though a wrapped ETH token is an ERC-20. If the exact token contract does not support the expected permit, use the app’s standard approval path rather than signing an unrelated or unfamiliar message.
A permit can save a transaction, but not the bridge transaction
Signing typed data happens off-chain and does not itself cost network gas. Submitting the permit does cost gas, usually as part of the transaction that also pulls tokens; bundling can avoid a separate approval transaction. It does not remove the bridge transaction, and the combined call can use more gas than a simple transfer. You still need the source chain’s native gas token to pay for transactions unless the application provides another supported payment method.
A less obvious edge case occurs when someone submits a valid permit before the bridge transaction does. EIP-2612 permits can be submitted by any address, so a third party can use the signature to set the intended allowance first. The signature is then consumed and a bridge call that blindly tries to submit it again may fail on the nonce. The tokens are not transferred merely because the permit was submitted; the spender still needs an allowance and must make the token pull. When a combined flow fails, check the token’s current allowance and nonce before signing again, and use the normal approval route if the application cannot handle an already-used permit.
In practice, the shortest safe path is to confirm the token contract and source chain, review the spender and amount in the permit, and sign only if those fields match the bridge action you started. Then submit the bridge transaction and keep enough source-chain gas for it. A permit changes how the allowance is authorized; it does not change the bridge’s cross-chain transfer mechanism.