The Avalanche Bridge charges transfer fees in order to cover the cost of the transaction fees on the Avalanche and Ethereum networks, as well as the operational costs of the bridge infrastructure. These fees are charged in-kind with the ERC20 asset being transferred. That is when you transfer a token, a portion of the balance transferred goes towards covering the fee.
When moving assets from Ethereum to Avalanche, the bridge fee is currently $3 worth of the ERC20 asset being transferred. Please note that the Avalanche Bridge only allows transfers to the same address on the other network. After the asset is transferred to the other network, it can then be sent to any address or contract.
When moving assets from Avalanche to Ethereum, the bridge fee is largely based on the **expected** Ethereum transaction fee. This is calculated using current asset prices, the current Ethereum gas price, and the approximate amount of gas that will be used by the Ethereum transaction. As such, the Ethereum transaction fee, and thus also the bridge fee, can be highly variable. To account for price volatility, a constant dollar amount (currently $20) is added to the bridge fee.
The bridge will not process any transfers that are less than the current estimated fee amount. If a bridge transfer is not going through for a small amount this could potentially be the issue. It would be recommended to check current network fees, and increase the amount for the bridge transaction before proceeding.
The reason for this is to protect the user from accidentally bridging a small amount, and not having enough to cover the network fee. This Al’s protects from network surges in between the transaction being initiated and when it completes.
On Avalanche, transaction fees are paid in the native asset, AVAX. In order to send transactions on the Avalanche C-Chain, there must be sufficient AVAX in the wallet to cover the cost of the gas for the transaction. To help users get started, the Avalanche Bridge will airdrop a small amount of AVAX for transactions of $75 or more (subject to change) worth of tokens over from Ethereum. In order to avoid running out of AVAX to cover transaction fees, it is recommended to purchase additional AVAX after bridging.
Note: The bridge fee will be different than the Ethereum transaction fee displayed in explorers such as Etherscan because asset prices, the Ethereum gas price, and the amount of gas used by Ethererum transactions fluctuate. The expected bridge fee is displayed in the bridge UI when performing a transfer.