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Header Subquery

Description​

The header subquery provides data from a past block's header.

Limits​

Maximum of 128 header subqueries.

Usage​

To access data from the block header of block number blockNumber, you must first construct a Header object using the getHeader function:

const getHeader: (blockNumber: number | CircuitValue) => Readonly<Header>;

The returned Header is an interface with the functions below. Note that all functions in the interface are async.

Example Usage​

Here is an example of how to use the Header interface:

const header: Header = getHeader(blockNumber);
const gasLimit: CircuitValue256 = await header.gasLimit();

Header Interface​

parentHash: () => Promise<CircuitValue256>;

Returns the parent hash of the block.

sha3Uncles: () => Promise<CircuitValue256>;

Returns the hash of the uncles, also known as the ommers hash. For blocks after EIP-3675 (Proof of Stake), this is the fixed constant 0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347.

miner: () => Promise<CircuitValue256>;

Returns the address to which priority fees for this block are transferred. Also known as the beneficiary, coinbase, or fee recipient.

stateRoot: () => Promise<CircuitValue256>;

Returns the root of the state trie of the block.

transactionsRoot: () => Promise<CircuitValue256>;

Returns the root of the transaction trie of the block.

receiptsRoot: () => Promise<CircuitValue256>;

Returns the root of the receipts trie of the block.

logsBloom: (logsBloomIdx: ConstantValue) => Promise<CircuitValue256>;

This requires an additional input logsBloomIdx which must be in [0,8). It will return the 32 bytes chunk in range [32 * logsBloomIdx, 32 * (logsBloomIdx + 1)) of the logsBloom of the block.

difficulty: () => Promise<CircuitValue256>;

Returns the difficulty of the block. After EIP-3675 (Proof of Stake), this is the fixed constant 0.

number: () => Promise<CircuitValue256>;

Returns the block number.

gasLimit: () => Promise<CircuitValue256>;

Returns the gas limit of the block.

gasUsed: () => Promise<CircuitValue256>;

Returns the total gas used by all transactions in the block.

timestamp: () => Promise<CircuitValue256>;

Returns the block timestamp.

extraData: () => Promise<CircuitValue256>;

Returns the extra data of the block.

mixHash: () => Promise<CircuitValue256>;

Returns the mix hash of the block. After EIP-4399 (The Merge), the mix hash returns the Beacon chain RANDAO of the previous block.

nonce: () => Promise<CircuitValue256>;

Returns the block nonce. After EIP-3675 (Proof of Stake), this is the fixed constant 0x0000000000000000.

baseFeePerGas: () => Promise<CircuitValue256>;

Only callable on blocks after EIP-1559. Returns the base fee per gas in the block.

withdrawalsRoot: () => Promise<CircuitValue256>;

Only callable on blocks after EIP-4895 (Shanghai). Returns the withdrawals root of the block.