What are the current best practices for using cross-chain bridges in DeFi?
Moving assets between blockchains has gone from a niche developer curiosity to an everyday DeFi necessity. Whether you're chasing better yields on Arbitrum, tapping into a new protocol on Base, or simply managing a multi-chain portfolio, cross-chain bridges have become the connective tissue of the modern DeFi ecosystem.
But here's the uncomfortable truth: bridges are also one of the most dangerous places to put your assets. They've been hacked, drained, and exploited more than almost any other type of DeFi infrastructure. Over $2.3 billion was lost to bridge exploits in 2025 alone - already surpassing the entirety of 2024's losses.
That's not a reason to avoid bridges entirely - it's a reason to use them more intelligently. This guide covers what bridges actually are, how they work under the hood, and the best practices that separate savvy cross-chain users from the ones who end up in a post-mortem thread.
What is a cross-chain bridge?
Think of blockchains like separate islands. Ethereum is one island. Arbitrum is another. Base, Polygon, Solana - each its own ecosystem with its own rules, assets, and community. By default, they don't talk to each other.
A bridge is the ferry service between those islands. It's a protocol that lets you transfer digital assets from one blockchain to another - without it, moving ETH from Ethereum to Optimism, or onto Solana, would simply be impossible.
Underneath that simple description, bridges are actually remarkably complex pieces of infrastructure. To move an asset from Chain A to Chain B, something has to be locked, minted, verified, or relayed across two environments that were never designed to communicate. And that complexity is precisely why they attract attackers.
How do bridges actually work?
There are a few different architectural models in common use:
Lock-and-mint bridges lock your original token in a smart contract on the source chain and mint a "wrapped" equivalent on the destination chain. It's the most common model, and it works well - until the lock contract gets exploited, at which point the wrapped tokens on the other end can become worthless. This is what happened in some of the biggest bridge hacks in DeFi history.
Liquidity pool bridges (used by protocols like Stargate and Hop) work differently. Rather than locking and minting, users deposit assets into a liquidity pool on the source chain and withdraw equivalent assets from a pool on the destination chain, with liquidity providers incentivized through staking rewards to keep pools adequately filled. This approach avoids wrapped tokens but introduces its own risk: pool imbalances and liquidity crunches.
Intent-based bridges (the newer generation, used by Across Protocol and Cow Swap!) flip the model entirely. They allow users to simply specify what they want to happen - the end result - rather than how it should happen, with a competitive network of relayers bidding to fill the order and a settlement layer verifying fulfillment. This abstracts away the technical complexity while keeping the security model relatively clean.
Understanding which type of bridge you're using matters, because each carries different failure modes.
The risks you need to understand
Before we get to best practices, it's worth being honest about what you're dealing with.
Smart contract vulnerabilities are the big one. Bridges require complex smart contracts on two separate chains to stay in sync. Any bug in that logic is a potential jackpot for an attacker. The Wormhole hack (2022, $320 million), the Ronin Bridge hack ($624 million), and the Nomad collapse ($190 million) all stemmed from smart contract flaws of one kind or another. These aren't ancient history - they're a reminder of what's still possible.
Private key compromise is another major vector. Private key vulnerabilities are behind some of Web3's most notorious cross-chain bridge hacks, often due to poor private key management or operational security practices. When a bridge relies on a small, centralised set of validators, compromising those keys can mean draining the entire bridge.
Liquidity imbalances are less dramatic but still painful. If many users bridge assets in one direction and few do the reverse, pools become unbalanced - leading to delays, failed transactions, and price discrepancies that arbitrageurs exploit at your expense.
Fake bridges and phishing round out the risks. With so many bridge interfaces available, scam sites that mimic legitimate bridges are common. You approve a transaction thinking you're bridging - and you've just handed your wallet over.
Best practices for bridging safely
1. Do your homework on the bridge itself
Not all bridges are created equal. Before trusting a bridge with your assets, spend five minutes on due diligence:
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Check for independent security audits. Multiple audits from reputable firms are a baseline expectation for any bridge worth using. Smart contract bridges should have undergone multiple reviews by top-tier security firms. If a bridge can't point you to audit reports, that's a red flag.
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Look for a bug bounty program. Active bug bounty programs signal that a team takes security seriously and has incentivised the wider community to find vulnerabilities before attackers do.
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Check their track record. Has the bridge been exploited before? How did the team respond? A protocol that was hacked and handled it responsibly - patching quickly, compensating users - can be more trustworthy than one that's never been tested at all.
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Assess how decentralised the validators are. The more servers, infrastructure providers, locations, and operators involved, the more a bridge and its private keys are protected against single points of failure and centralisation risks.
2. Prefer non-custodial, trust-minimised architectures
When you use a custodial bridge, you're trusting the operator to behave honestly and to keep their private keys secure. When you use a non-custodial bridge, your assets are secured by smart contract logic and cryptographic guarantees rather than human operators.
All else being equal, trust-minimised architectures - particularly those using zero-knowledge proofs or native light-client verification - offer stronger security guarantees. These have a strong trust model because security depends on cryptography and consensus rather than external signers - though they come with higher gas costs and more engineering complexity, making them best suited for high-value treasury moves that prioritise trust minimisation over speed.
3. Never bridge more than you can afford to lose in a single transaction
This sounds harsh, but it's genuinely sensible risk management. Bridges remain high-risk infrastructure. Even the most audited, well-regarded bridge carries non-zero risk.
If you need to move a large amount, consider breaking it into smaller transactions over time. You'll pay slightly more in fees, but you're limiting your maximum exposure in any single bridge event. Users must treat bridges as high-risk infrastructure, conducting thorough due diligence, limiting transfer sizes, and utilising insurance when available.
4. Verify everything before you sign
This is table stakes for all of DeFi, but it bears repeating in the context of bridges:
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Always navigate directly to the bridge's official URL - don't click links in Discord, Telegram, or Twitter DMs
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Bookmark the interfaces you use regularly so you're not Googling "X bridge" and accidentally landing on a phishing clone
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Read the transaction prompt carefully before signing - what are you actually approving?
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If you're sending to a custom recipient address on the destination chain, triple-check that address. Cross-chain transactions are largely irreversible once the bridge deposit is submitted
5. Know your fees before you bridge
Bridge fees aren't just the gas on the source chain. You'll typically encounter: gas on the source chain, a bridge provider fee for processing your transfer, and gas on the destination chain. These stack up, and on congested networks, they can make small transfers economically unviable.
Before bridging, get a clear picture of the total cost - including what you'll receive on the other end, not just what you're sending. And always make sure you'll have enough native gas tokens on the destination chain to actually use your assets once they arrive. Landing on Base with USDC but zero ETH for gas is a common and avoidable frustration.
6. Consider using a bridge aggregator
Rather than manually selecting a bridge and hoping you picked the right one, bridge aggregators do the heavy lifting for you. Bridge aggregators are platforms that combine multiple bridges to provide users with the most efficient option for cross-chain transfers, considering factors like cost, speed, slippage, and security - working similarly to how DEX aggregators work for token swaps.
This matters because the "best" bridge for any given transfer depends on which asset you're moving, which chains are involved, current liquidity conditions, and gas prices. A good aggregator evaluates all of this in real-time and routes you to the optimal path - rather than leaving you to figure it out manually with multiple tabs open.
7. After bridging: revoke unused approvals
If you've approved a bridge contract to spend your tokens, that approval doesn't automatically expire. It sits there, potentially open, even long after your transfer is complete. Periodically reviewing and revoking old approvals - using a tool like Revoke.cash - is good hygiene for any DeFi user, especially one who bridges regularly.
The direction things are heading
Bridge security and usability are both improving. Zero-knowledge proof bridges, which validate cross-chain messages cryptographically rather than relying on trusted intermediaries, represent a significant step forward in the trust model.
Intent-based architectures meanwhile, are making the user experience dramatically simpler while keeping execution competitive. And as the multi-chain ecosystem matures, infrastructure like canonical bridges and native asset transfers are reducing reliance on the wrapped-token model that has caused so many headaches.
As newer security models like ZK bridges and shared security mature, and as formal verification becomes standard practice, bridge security is expected to improve substantially. But cross-chain communication is inherently complex, and bridges will remain attractive targets as long as they hold significant value.
The practical implication: be appropriately cautious, do your research, and don't let convenience override security.
How CoW Swap fits in
One of the core frustrations with cross-chain trading has always been the multi-step juggling act - bridge here, swap there, pay gas twice, hope prices don't shift in between.
CoW Swap has tackled this head-on by evolving from a DEX aggregator into a bridge aggregator too. When you initiate a cross-chain trade on CoW Swap, it automatically chooses the optimal bridge route from trusted providers and bundles it all into one seamless, gasless transaction. You express a single intent - "I want to swap USDC on Arbitrum for ETH on Base" - and CoW Swap's solver network handles the entire route, safely and efficiently, in one flow.
The same MEV protection that CoW Protocol is known for on single-chain swaps extends to cross-chain trading too - so you're not exposing yourself to front-running or sandwich attacks mid-transfer. And because CoW Swap integrates multiple bridge partners (currently including Bungee and Near Intents, with more to come), you're not locked into a single bridge's liquidity or reliability.
It's the kind of experience cross-chain trading should have always been: one intent, one flow, best route.
👉 Try cross-chain swaps on CoW Swap
