chain_getBlockHash - Acala RPC Method

Returns the block hash for a given block number on Acala. This is the primary method for converting block numbers into block hashes, which are required by most other chain RPC methods.

Why Acala? Build on Polkadot's DeFi and liquidity hub with aUSD stablecoin and liquid staking (LDOT) with $250M aUSD ecosystem fund, 150%+ LDOT TVL growth, micro gas fees payable in any token, and Coinbase Cloud partnership.

When to Use This Method

chain_getBlockHash is fundamental for DeFi developers, stablecoin builders, and teams requiring cross-chain liquidity:

• Historical Queries — Convert block numbers to hashes for state queries at specific heights on Acala
• Block Navigation — Navigate the blockchain history for decentralized stablecoin (aUSD), liquid DOT staking (LDOT), and cross-chain AMM DEX
• Data Indexing — Build block number-to-hash mappings for indexers and explorers
• Cross-Reference — Translate block numbers from events or logs into hashes for detailed lookups

Code Examples

Common Use Cases

1. Block Range Iterator

Iterate over a range of blocks on Acala for indexing:

async function iterateBlocks(api, startBlock, endBlock) {
  for (let num = startBlock; num <= endBlock; num++) {
    const hash = await api.rpc.chain.getBlockHash(num);
    const block = await api.rpc.chain.getBlock(hash);

    console.log(`Block #${num}: ${block.block.extrinsics.length} extrinsics`);
  }
}

2. Historical State Query

Query Acala state at a specific block height:

async function getBalanceAtBlock(api, address, blockNumber) {
  const blockHash = await api.rpc.chain.getBlockHash(blockNumber);
  const apiAt = await api.at(blockHash);
  const account = await apiAt.query.system.account(address);

  return {
    blockNumber,
    free: account.data.free.toString(),
    reserved: account.data.reserved.toString()
  };
}

3. Genesis Hash Verification

Verify you are connected to the correct Acala network:

async function verifyNetwork(api, expectedGenesisHash) {
  const genesisHash = await api.rpc.chain.getBlockHash(0);

  if (genesisHash.toHex() !== expectedGenesisHash) {
    throw new Error(`Wrong network! Expected ${expectedGenesisHash}, got ${genesisHash.toHex()}`);
  }

  console.log('Connected to correct network');
}

Error Handling

Related Methods

• chain_getBlock — Get full block data by hash
• chain_getHeader — Get block header by hash
• chain_getFinalizedHead — Get the latest finalized block hash