Overview
What Axelar is, and how these docs are organized.
Axelar is an interoperability network: it connects blockchains so that applications on one chain can call contracts and move tokens on another. This page covers the Axelar chain itself, how it verifies the chains connected to it, Amplifier, and the protocols applications build on.
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An L1 blockchain
The Axelar network is its own proof-of-stake blockchain, built with the Cosmos SDK. Validators produce blocks and secure the chain with staked AXL. Anyone can run a node, query it over RPC or follow it in an explorer, and like any L1 the chain goes through network upgrades and governance proposals.
The chain is the hub of a hub-and-spoke network. Other blockchains, the connected chains, connect to Axelar rather than to each other: a message from one connected chain to another passes through Axelar, which checks it and routes it to its destination. A chain that connects to Axelar can reach every other connected chain.
Public RPC, LCD and gRPC endpoints, block explorers and faucets for mainnet and testnet are listed on Network.
Verifying connected chains
Before Axelar passes a message on, it checks that the message really happened on its source chain: everyone who verifies that chain queries their own node for it and votes. Who votes depends on how the chain is connected:
- Consensus chains, the EVM chains connected before Amplifier, are verified by the Axelar validators.
- Amplifier chains are verified by Amplifier verifiers, who don't need to be validators.
See Verifiers for how to take part in either.
A cross-chain protocol: Amplifier
Amplifier is how new chains connect to Axelar, permissionlessly. It is a set of CosmWasm contracts on the Axelar chain, plus the off-chain verifier service:
- A gateway contract on each connected chain is where applications send and receive cross-chain messages.
- On Axelar, a verifier contract for each chain counts the verifiers' votes, a router forwards the message to the destination chain, and a prover produces the proof the destination gateway needs to accept it.
Protocols for applications
Applications use two cross-chain protocols that run on Axelar, on both kinds of chain:
- General Message Passing (GMP) sends arbitrary messages between chains, so a contract on one chain can call a contract on another.
- Interchain Token Service (ITS) uses GMP to deploy tokens and transfer them across chains, routed through the ITS Hub on Axelar.