Crypto Bridges Require Gas on the Sending Chain

To bridge crypto, keep the source chain’s native token in your wallet to submit the transaction; whether you need gas on the destination chain depends on the route. Ethereum.org explains that gas measures the computation a transaction uses and that Ethereum fees are paid in ETH, even when the transaction moves another token.

What gas token does a bridge use?

You pay the sending network’s fee in that network’s accepted gas token, not necessarily in the asset you are bridging. The bridge interface and your wallet show the network and estimated fee before you sign; check both, especially if your token is on more than one chain.

A token approval may be a separate transaction before the bridge deposit, so the wallet can ask you to sign and pay for two transactions. Some routes combine or avoid that approval, but the wallet’s prompts determine what your transfer requires. For an explanation of the transfer mechanics, read how AcrossBridge moves crypto across chains.

Do I need gas on both chains?

You need enough source-chain gas to complete the actions the route requests. Destination gas is a separate question: some bridge routes arrange delivery or cover the destination-side transaction, while others leave you with tokens and require the destination network’s native token for anything you do next. Check the route’s quote and delivery details; Across’s fee documentation, for example, lists destination-chain fill costs as a distinct fee component.

• Keep the source chain’s gas token available for the deposit and any required approval.
• Check whether the quote includes destination gas or delivers a gas token.
• If you plan to swap, transfer, or use the received tokens, leave or acquire the destination chain’s native gas token.
• Confirm the destination network in your wallet before using the bridged asset.

How much gas should I leave in my wallet?

Use the wallet’s live estimate rather than a fixed amount: fees change with network demand, and contract interactions can use more gas than a simple transfer, as Ethereum.org notes. Keep enough for every transaction shown in the wallet, including a possible approval, and avoid sending the full balance if that balance includes the gas token.

The practical rule is to fund the source chain first, then check the specific route for destination gas. The bridge quote and wallet prompts will show what is required before you confirm; whether the destination transaction is covered depends on the route and remains unconfirmed until you inspect those details.