> For the complete Linea documentation index, see [llms.txt](/llms.txt). > Agents can fetch this page as Markdown at [https://docs.linea.build/api/linea-smart-contracts/messageservice/l1/l1messageservice.md](https://docs.linea.build/api/linea-smart-contracts/messageservice/l1/l1messageservice.md). # L1MessageService # `L1MessageService` ### systemMigrationBlock ```solidity uint256 systemMigrationBlock ``` _This is currently not in use, but is reserved for future upgrades._ ### __MessageService_init ```solidity function __MessageService_init(uint256 _rateLimitPeriod, uint256 _rateLimitAmount) internal ``` Initialises underlying message service dependencies. #### Parameters | Name | Type | Description | | --- | --- | --- | | _rateLimitPeriod | uint256 | The period to rate limit against. | | _rateLimitAmount | uint256 | The limit allowed for withdrawing the period. | ### sendMessage ```solidity function sendMessage(address _to, uint256 _fee, bytes _calldata) external payable ``` Adds a message for sending cross-chain and emits MessageSent. _The message number is preset (`nextMessageNumber`) and only incremented at the end if successful for the next caller. This function should be called with a `msg.value` equal to `_value` plus `_fee`. The fee will be paid on the destination chain._ #### Parameters | Name | Type | Description | | --- | --- | --- | | _to | address | The address the message is intended for. | | _fee | uint256 | The fee being paid for the message delivery. | | _calldata | bytes | The calldata to pass to the recipient. | ### claimMessageWithProof ```solidity function claimMessageWithProof(struct IL1MessageService.ClaimMessageWithProofParams _params) external ``` Claims and delivers a cross-chain message using a Merkle proof. _if tree depth is empty, it will revert with L2MerkleRootDoesNotExist. if tree depth is different than proof size, it will revert with ProofLengthDifferentThanMerkleDepth._ #### Parameters | Name | Type | Description | | --- | --- | --- | | `_params` | `struct IL1MessageService.ClaimMessageWithProofParams` | Collection of claim data with proof and supporting data. | ### sender ```solidity function sender() external view returns (address originalSender) ``` Claims and delivers a cross-chain message. _The message sender address is set temporarily in the transient storage when claiming._ #### Return Values | Name | Type | Description | | --- | --- | --- | | originalSender | address | The message sender address that is stored temporarily in the transient storage when claiming. | Contributions not accepted These reference pages are automatically generated based on Linea's [smart contracts](https://github.com/Consensys/linea-monorepo/tree/main/contracts/src). To ensure they accurately match the deployed smart contracts, we cannot accept any contributions that edit these pages.