The state of cross-chain: How Across saves on gas fees and why that matters
Tldr; As Across takes an optimistic approach to confirming cross-chain transactions, it’s extremely gas-efficient. This results in lower costs for users, which should serve Across well in the future.
Key takeaways:
- Across optimizes for gas efficiency by leveraging UMA’s optimistic oracle to confirm transactions.
- Relayers cover gas fees on behalf of users and then charge them a fee for filling their orders.
- Recent activity shows that Across spends up to 80% less on gas than other cross-chain bridges.
As the crypto ecosystem has grown, the demand for cross-chain interoperability solutions has soared. In the multi-chain world, users need to be able to move their assets between Ethereum and other chains, and they need their orders filled as quickly and cheaply as possible. This means the 100+ cross-chain bridges in the ecosystem need to save on gas costs if they want to best serve their users.
As our recent data studies have shown, Across is the world’s fastest cross-chain bridge, and it also routinely ranks as the cheapest. This is thanks in part to its capital-efficient design and in part to its low gas expenditures. Across has lower gas expenditure than its competitors because of its optimistic approach, which results in lower fees for users.
We recently looked at the numbers to see how Across and other bridges rank on gas spending. Our findings led us to the following conclusion: Across is the most gas-efficient bridge, and that strengthens our conviction that it will beat its competitors in the long term.
In this piece, we compare gas expenditures for bridge transfers to and from the most active blockchain network. We also explain how Across consistently saves on fees versus other bridges, and what this could mean for the future of the cross-chain ecosystem.
Across’ gas spending in numbers
Across helps users move their assets between Ethereum and Layer 2 chains at a high speed and low cost. For the purposes of this piece, we looked at gas spending for USDC on Ethereum mainnet in August 2023.
Our findings were robust across a variety of metrics, including median and mean gas expenditures, and the chain we computed on. We focused on the minimum gas expenditure on Ethereum because we think it is the most impactful component due to Ethereum’s higher gas prices.
For deposits on Ethereum (i.e. where Ethereum is the origin chain), Across had a minimum gas expenditure of 76,130 units, the lowest of all its competitors. The most gas-intensive bridge was Stargate, whose minimum expenditure was 367,349 units. In other words, Across ranked as the most gas-efficient bridge for Ethereum deposits, consuming about 80% less gas than the top spender.
For order fills on Ethereum (i.e. where Ethereum is the destination chain), Across had a minimum gas expenditure of 95,981 units, the lowest of all its competitors. The next best performer was Hop, whose minimum expenditure was 136,120 units. cBridge, Stargate, and Synapse all spent over twice as much as Across on order fills on Ethereum.
In short, the numbers show that Across is the most gas-efficient bridge for deposits and orders on Ethereum.
How Across saves on gas fees
When we were building Across, we meticulously scrutinized the code to make as many optimizations as possible. Just as Uniswap built the DEX with the lowest gas fees and then came out on top in DeFi summer, we held off on launching Across until we were sure it would be the cheapest bridge solution.
The onchain logic of the bridge is about as near to optimal as possible. The onchain logic of the bridge is about as near to optimal as possible. A transfer requires only an ERC-20 token transfer (~45k gas) and a relayer repayment, which equates to a fraction of the gas fee for an ERC-20 transfer. Because the aggregation is done offchain and verified optimistically, the per-transaction cost falls with more transactions.
As Across’ gas expenditure is low, the burden funneled down to users is also low. When Across users want to bridge their assets, they wait for relayers to fill orders, and then LPs refund relayers via a single liquidity pool on Ethereum mainnet. Relayers compete to fill the user’s order on their requested destination chain, covering gas costs and charging the user a fee. They effectively loan out their assets and rely on UMA’s optimistic oracle for validation then wait to get reimbursed by LPs.
Because Across takes an optimistic approach, it can confirm transactions without needing any gas-intensive onchain validation. This explains how Across spends less on gas than its competitors to move assets between blockchains.
Across and the cross-chain future
Across took several crucial design decisions that differentiate it from its competitors. Across leverages UMA’s optimistic oracle to verify transactions for relayers and reduce its gas expenditure. In turn, the user gets their order filled quickly and cheaply.
Across’ design is key to helping users move tokens across chains extremely efficiently. While arbitrary messaging systems have recently been in vogue in the cross-chain space, we’ve long held onto the belief that Across’ optimistic approach is the winning one. Our recent findings tell us that Across is the fastest, cheapest, and most gas-efficient bridge — and aggregator volumes reflect its strength versus competitors.
The cross-chain ecosystem is still in its infancy, but we believe that fundamentals will increasingly matter as the space grows. As aggregators grow and new products offer easier access to Web3, bridges will be abstracted from users. These tools will simply serve users the optimal solution for their transfer instead, which is why Across is set to thrive. Though it’s still early, the winning bridge will be the bridge that wins on tech. And that’s why we’re so confident in Across’ continued success.
The data for this piece was compiled by Across Protocol’s data and research team. It specifically examines USDC transfers to and from Ethereum in August 2023. It also excludes canonical bridges as regular users typically favor non-canonical bridges.
