Guards

Add programmable pre- and post-execution checks to Safe Smart Accounts to enforce custom transaction restrictions.

Safe Guards were introduced in Safe contracts version 1.3.0.

Safe Guards add an additional security layer on top of Safe’s n-out-of-m multi-signature scheme. They allow Safe owners to define custom rules that determine whether a transaction should be allowed to execute.

A Safe Guard can perform checks:

• Before execution, to validate the transaction parameters and context
• After execution, to verify the final state of the Safe once the transaction has completed

Pre-execution checks can inspect all transaction parameters—such as the target address, calldata, value, and operation type—and decide whether the transaction should proceed.
Post-execution checks run at the end of the transaction and can be used to assert invariants or detect unexpected state changes.

Guards are commonly used to:

• restrict interactions to approved contracts
• enforce protocol-specific invariants
• add additional safety checks around sensitive operations

To explore real-world examples of Safe Guards, see:

• Zodiac Guard implementations
• Yearn Guard design

Important: Safe Guards are security-critical. Because a Guard can block transaction execution entirely, a faulty or malicious Guard can cause a denial of service and lock funds in a Safe. Only use well-reviewed and audited Guards, and always consider recovery mechanisms.