What is a meta-transaction?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 5 min
In short
A meta-transaction is one where the user signs the intent and a third party relays it on-chain. Decoupling the signer from the sender is what makes fee sponsorship possible. The flip side: once signed, the payload is in someone else's hands and you no longer control when it executes.
Key points
- Separates the signer from the sender
- It is the basis on which fee sponsorship works
- The signed payload is itself the authorisation
- The signer cannot control when it executes
Definition
A transaction in which the user signs the intended action and a relayer broadcasts it, paying the fee. The contract recovers the original actor from the signature.
In a normal transaction the signer is also the sender and pays the fee. A meta-transaction splits these: the user signs the intended action, a relayer wraps it and broadcasts it, and the contract verifies the signature to determine who the real actor is.
That separation lets a user act without holding the native coin, and it also allows several users' actions to be batched into one transaction. Standards such as ERC-2771 exist to check that the relayer is reporting the original signer honestly.
The design point to watch is replay. Sending the same signature twice would run the action twice, so signatures carry a nonce and an expiry. A contract that fails to verify these properly can be made to execute the same intent more than once.
Watch out for
- · What you sign is the authorisation itself — never sign without reading it
- · A relayer can sit on your signature, delay it, or never submit it at all
- · Assume execution may come after the market moves; keep expiries short