chain_getBlockHash - Hydration RPC Method

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

Why Hydration? Build on Polkadot's leading DEX with $200M+ TVL, Omnipool AMM, and native HOLLAR stablecoin with Omnipool with reduced slippage, permissioned listings, 3M DOT DAO allocation, and 200%+ APR farm yields.

When to Use This Method

chain_getBlockHash is fundamental for DeFi developers, liquidity providers, and DAOs requiring capital-efficient trading:

• Historical Queries — Convert block numbers to hashes for state queries at specific heights on Hydration
• Block Navigation — Navigate the blockchain history for single-sided liquidity provision, cross-chain trading (SOL, KSM, tBTC), and HOLLAR decentralized stablecoin
• 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 Hydration 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 Hydration 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 Hydration 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