Is Relay Safe? Non-Custodial Crosschain Explained

Mar 11, 2026

4 min read

Any protocol moving value across blockchains gets a simple question: where do the funds go in transit?

With Relay, the answer is: they don't go anywhere. The protocol never takes custody of your assets.

The Non-Custodial Model

Traditional bridges take custody of funds in the process of moving them. You deposit ETH on Ethereum, the bridge holds it, and issues wrapped ETH on the destination chain. The bridge contract — and often a multisig controlling it — holds the pooled deposits. This is where historic bridge exploits have occurred: attacking the contracts holding the pooled funds.

Relay uses a different model entirely: intent-based execution. You don't deposit funds into a bridge contract. Instead, you sign a transaction specifying your desired output — the token and chain you want to receive. A network of independent fillers monitors these intents and competes to fill them. The filler delivers your requested output to your destination address directly, then claims the input from the protocol as reimbursement.

Your funds move from your wallet to your destination wallet. There is no pool, no bridge contract holding your deposits, and no centralised custodian.

What Fillers Are

Fillers are independent entities — typically professional market makers or automated solvers — that provide the liquidity to execute crosschain intents. They pre-fund the destination chain, deliver the requested output to the user's wallet, and are repaid from the input amount.

Fillers take on the execution risk, not users. If a filler fails to deliver, the protocol ensures the user's funds are returned. Fillers must meet the output specification exactly or the transaction reverts — there's no partial execution that can leave funds in an ambiguous state.

What Happens If a Transaction Fails

Relay's execution model provides a safety guarantee: if the intent cannot be filled, the transaction does not proceed. You cannot be left in a state where you've sent funds but haven't received the output.

If no filler picks up an intent, it expires and no funds move. If a filler attempts to fill but can't complete — due to gas issues, routing problems, or other failures — the transaction reverts. In all cases, the user's starting position is preserved.

This is meaningfully different from legacy bridges where failures could leave funds stuck in intermediate states for hours or days, requiring manual intervention.

Protocol Track Record

Relay has processed over $20B in volume across 85+ chains, with a 99.9%+ fill rate. At this scale, the protocol has been tested across market conditions, chain outages, gas price spikes, and liquidity events.

There have been no exploits of Relay's core protocol. The non-custodial model significantly reduces the attack surface: there are no large pooled deposits to target, and each user's transaction is executed atomically.

Smart Contract Risk

Like any on-chain protocol, Relay's smart contracts carry inherent risk. Smart contract code can have bugs, and the blockchain environment can produce unexpected edge cases. This is a category of risk that exists for any protocol.

Relay's architecture minimises this risk through:

• No pooled liquidity in protocol contracts (removes the primary exploit target)
• Atomic execution guarantees (no intermediate custody states)
• An established security review process

For users doing large transactions, the same risk calculus applies as with any DeFi protocol: the non-custodial model and track record are meaningful signal, but smart contract risk can never be fully eliminated.

Comparing to Alternatives

Centralised exchanges hold custody of your funds by definition. You're trusting the exchange's solvency, security, and policies. Relay is fully non-custodial.

Legacy bridges hold pooled deposits in smart contracts — the attack surface responsible for billions in bridge exploits historically. Relay's model has no pooled deposits.

Other intent-based protocols share architectural similarities with Relay. The key differentiators are execution speed (2.7 second median), chain coverage (85+), volume ($20B+), and fill rate (99.9%+).

Frequently Asked Questions

Can Relay access or freeze my funds?

No. Relay never holds your funds. You sign a transaction from your own wallet, and the output arrives at your specified destination address. There is no central entity with access to your assets during the process.

Has Relay been audited?

Relay's protocol and contracts undergo security reviews. For specific audit details, see the official Relay documentation at relay.link.

What if I send to the wrong address?

Blockchain transactions are irreversible. Always verify your destination address before confirming. Relay cannot reverse transactions.