| Aggregation ISM (Static) | Composition | In Production | Combines multiple ISMs together, requiring all or a k‑of‑n subset to agree for validation. |
| Aggregation ISM (Storage) | Composition | In Production | Combines multiple ISMs together, requiring all or a k‑of‑n subset to agree for validation. The module set and threshold are stored in state and can be updated after deployment. |
| Routing ISM | Composition | In Production | Directs messages to different ISMs depending on the origin domain. |
| Amount Routing ISM | Composition | In Production | Routes messages to different ISMs based on the amount of the transfer. |
| Fallback Routing ISM | Composition | In Production | Provides a backup ISM path if the origin domain is not configured in the routing map. |
| ICA Routing ISM | Composition | In Production | Routes messages through Interchain Accounts (ICA). |
| Pausable ISM | Composition | In Production | Allows message flow to be paused in emergencies. |
| Rate Limited ISM | Composition | In Production | Uses a token bucket rate limiter to throttle the amount that can be sent via HWR within a given time interval. Only applies to HWR applications/message encoding. |
| Merkle Root Multisig ISM | Security | In Production | Verifies k‑of‑n signatures on a Merkle root and employs Merkle proofs of message IDs in this root. |
| Merkle Root Multisig ISM (Storage) | Security | In Production | Verifies k‑of‑n signatures on a Merkle root and employs Merkle proofs of message IDs in this root. The module set and threshold are stored in state and can be updated after deployment. |
| Message ID Multisig ISM | Security | In Production | Verifies k‑of‑n signatures on a message ID. The signatures are from the checkpoint struct and are shared across related ISMs. |
| Message ID Multisig ISM (Storage) | Security | In Production | Verifies k‑of‑n signatures on a message ID. The signatures are from the checkpoint struct and are shared across related ISMs. The module set and threshold are stored in state and can be updated after deployment. |
| Weighted Merkle Root Multisig ISM | Security | In Development | A weighted voting system, extending Merkle Root multisig, where each signer’s influence is weighted by their stake. |
| Weighted Message ID Multisig ISM | Security | In Development | A weighted voting system on top of Message ID multisig. |
| Offchain Lookup ISM | Security | In Production | Functions as an abstraction for building verification logic that leverages external data sources for validation. |
| Chainlink CCIP ISM | Security | In Production | Leverages Chainlink CCIP to validate messages. |
| Arbitrum L2 to L1 ISM | Security | In Development | Verifies cross-chain messages from Arbitrum L2 to Ethereum L1 using Arbitrum’s native proof system. |
| OP Stack ISM | Security | In Production | Verifies cross-chain messages from OP Stack rollups using the OP Stack native security model. |
| Noop ISM / Test ISM | Security | In Production | ISM for testing purposes. |
| Trusted Relayer ISM | Security | In Production | Relies on a trusted relayer to deliver the message on the Mailbox. |
