---
title: BlockHeader
description: BlockHeader describes metadata about a block.
source_url:
  html: https://thru.org/docs/api-ref/grpc/messages/thru/core/v1/block-header/
  md: https://thru.org/docs/api-ref/grpc/messages/thru/core/v1/block-header.md
---

# BlockHeader

BlockHeader describes metadata about a block.

**Package:** `thru.core.v1`

## Fields

| Field | Type | # | Description |
| - | - | - | - |
| `slot` | `uint64` | 1 · optional | |
| `block_hash` | [`BlockHash`](https://thru.org/docs/api-ref/grpc/messages/thru/core/v1/block-hash.md) | 2 · optional | |
| `header_signature` | [`thru.common.v1.Signature`](https://thru.org/docs/api-ref/grpc/messages/thru/common/v1/signature.md) | 3 · optional | |
| `version` | `uint32` | 4 · optional | |
| `producer` | [`thru.common.v1.Pubkey`](https://thru.org/docs/api-ref/grpc/messages/thru/common/v1/pubkey.md) | 5 · optional | |
| `expiry_timestamp` | [`google.protobuf.Timestamp`](https://thru.org/docs/api-ref/grpc/messages/google/protobuf/timestamp.md) | 6 · optional | |
| `start_slot` | `uint64` | 7 · optional | |
| `expiry_after` | `uint32` | 8 · optional | |
| `max_block_size` | `uint32` | 9 · optional | |
| `max_compute_units` | `uint64` | 10 · optional | |
| `max_state_units` | `uint32` | 11 · optional | |
| `bond_amount_lock_up` | `uint64` | 12 · optional | |
| `block_time` | [`google.protobuf.Timestamp`](https://thru.org/docs/api-ref/grpc/messages/google/protobuf/timestamp.md) | 13 · optional | |
| `weight_slot` | `uint64` | 14 · optional | |
| `chain_id` | `uint32` | 15 · optional | |