chain_getBlockHash - Bittensor RPC Method

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

Why Bittensor? Build on the decentralized machine intelligence network built around subnets, TAO staking, and validator-miner coordination with Yuma Consensus, subnet-based specialization, dual Substrate and EVM surfaces, and onchain incentive coordination.

When to Use This Method

chain_getBlockHash is fundamental for AI/ML developers, subnet operators, and teams building decentralized machine learning applications:

• Historical Queries — Convert block numbers to hashes for state queries at specific heights on Bittensor
• Block Navigation — Navigate the blockchain history for decentralized AI inference, subnet-specific AI models, TAO staking, and cross-subnet AI collaboration
• 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 Bittensor 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 Bittensor 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 Bittensor 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