<p>The block header is 80 bytes:</p>

<ul>
<li>Version number: 4 bytes</li>
<li>Previous block header hash: 32 bytes</li>
<li>Merkle root: 32 bytes</li>
<li>Timestamp: 4 bytes</li>
<li>Bits: 4 bytes</li>
<li>Nonce: 4 bytes</li>
</ul>

<p>The merkle tree hashes all the transactions in the block, the bits field is used to compute the target hash for the header, finally, the nonce is used as a counter to generate new block headers from a given merkle tree.</p>

CC BY-SA 3.0
2017-07-11T22:59:10.047Z
2017-07-11T22:59:10.047Z
alcio
<p>What the title says above, but for more clarification I am asking whether the hash of the previous block header is part of what is hashed to create the header of the new block? Like what are all the components that are hashed together to get the block header hash?</p>

<p>Thanks.</p>

CC BY-SA 3.0
2017-07-12T06:11:07.060Z
possible duplicate of https://bitcoin.stackexchange.com/q/41610/5406, related: https://bitcoin.stackexchange.com/a/13347/5406
Murch
<block><hash><block-header>
Is the hash of the previous block included in the block header?
James P.
# Is the hash of the previous block included in the block header?

(Asked by: username_0 on 2017-07-11)

What the title says above, but for more clarification I am asking whether the hash of the previous block header is part of what is hashed to create the header of the new block? Like what are all the components that are hashed together to get the block header hash?

Thanks.

**Tags:** block, hash, block-header

> **Comments:**
> **username_1**: possible duplicate of https://bitcoin.stackexchange.com/q/41610/5406, related: https://bitcoin.stackexchange.com/a/13347/5406  

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## 1 answers

### Answer by username_2 on 2017-07-11. Score: 4 | Accepted answer

The block header is 80 bytes:

* Version number: 4 bytes
* Previous block header hash: 32 bytes
* Merkle root: 32 bytes
* Timestamp: 4 bytes
* Bits: 4 bytes
* Nonce: 4 bytes

The merkle tree hashes all the transactions in the block, the bits field is used to compute the target hash for the header, finally, the nonce is used as a counter to generate new block headers from a given merkle tree.


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