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Cross-chain messaging overview

The Arbitrum protocol and related tooling makes it easy for developers to build cross-chain applications; i.e., applications that involve sending messages from Ethereum to an Arbitrum chain, and/or from an Arbitrum chain to Ethereum.

Ethereum-to-Arbitrum messaging

Arbitrary L1 to L2 contract calls can be created via the Inbox's createRetryableTicket method; upon publishing the L1 transaction, the L2 side will typically get included within minutes. Happily / commonly, the L2 execution will automatically succeed, but if reverts, and it can be rexecuted via a call to the redeem method of the ArbRetryableTx precompile.

For details and protocol specification, see L1 to L2 Messages.

For an example of retryable tickets in action, see the Greeter tutorial, which uses the Arbitrum SDK.

Arbitrum-to-Ethereum messaging

Similarly, L2 contracts can send Arbitrary messages for execution on L1. These are initiated via calls to the ArbSys precompile contract's sendTxToL1 method. Upon confirmation (about 1 week later), they can executed by retrieving the relevant data via a call to NodeInterface contract's constructOutboxProof method, and then executing them via the Outbox's executeTransaction method.

For details and protocol specification, see L2 to L1 Messages.

For a demo, see the Outbox Tutorial.