<p>It is the same hash but reversed since bitcoin transmits data using little endian format (most significant byte last)</p>

CC BY-SA 3.0
2018-04-25T16:02:38.233Z
2018-04-25T16:02:38.233Z
Mike D
<p>Also of note, the present <a href="https://live.blockcypher.com/btc-testnet/block/000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943/" rel="nofollow noreferrer">testnet genesis</a>:</p>
<p>Big Endian (typical for blockchain explorers):</p>
<p><code>000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943</code></p>
<p>Little Endian (correct for <a href="https://learnmeabitcoin.com/technical/block-header" rel="nofollow noreferrer">block header</a>):</p>
<p><code>43497fd7f826957108f4a30fd9cec3aeba79972084e90ead01ea330900000000</code></p>

CC BY-SA 4.0
2024-02-29T08:49:11.147Z
2024-02-29T08:49:11.147Z
Lee
<p>They're exactly the same number; one is written in <a href="https://en.wikipedia.org/wiki/Endianness" rel="noreferrer">little endian</a> notation and the other is big endian.  Notice that the bytes (two-hex-digit pairs) are exactly reversed from one to the other.</p>

<p>Block explorers like blockchain.info usually expect big-endian for block hashes.  The proof-of-work requirement means that the <em>most</em> significant bits have to be zero, so big endian makes it easier to see this.</p>

CC BY-SA 3.0
2018-04-25T16:01:36.343Z
2018-04-25T16:01:36.343Z
Nate Eldredge
<p>From Lightning Network <a href="https://github.com/lightningnetwork/lightning-rfc/blob/master/00-introduction.md" rel="nofollow noreferrer">documentation</a>:</p>

<blockquote>
  <p>Used in several of the BOLT documents to denote the genesis hash of a target
  blockchain. This allows nodes to create and reference channels on
  several blockchains. Nodes are to ignore any messages that reference a
  chain_hash that are unknown to them. Unlike bitcoin-cli, the hash is
  not reversed but is used directly.</p>
  
  <p>For the main chain Bitcoin blockchain, the chain_hash value MUST be
  (encoded in hex):
  6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000.</p>
</blockquote>

<p>However this wiki entry about Bitcoin's <a href="https://en.bitcoin.it/wiki/Genesis_block" rel="nofollow noreferrer">genesis block</a> has </p>

<blockquote>
  <p>GetHash()      =
  0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f</p>
</blockquote>

<p>Indeed, inputting the latter value into blockchain.info yields <a href="https://blockchain.info/block-index/14849/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f" rel="nofollow noreferrer">Block 0</a>, while the former value cannot be found on blockchain.info.</p>

<p>Why does the value <code>6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000</code> appear in Lightning Network as "Bitcoin's genesis hash"?</p>

<lightning-network><hash><genesis-block><endianness>
What is Bitcoin's "genesis hash"?
ripper234
# What is Bitcoin's "genesis hash"?

(Asked by: username_0 on 2018-04-25)

From Lightning Network [documentation](https://github.com/lightningnetwork/lightning-rfc/blob/master/00-introduction.md):

> Used in several of the BOLT documents to denote the genesis hash of a target
> blockchain. This allows nodes to create and reference channels on
> several blockchains. Nodes are to ignore any messages that reference a
> chain\_hash that are unknown to them. Unlike bitcoin-cli, the hash is
> not reversed but is used directly.
>
> For the main chain Bitcoin blockchain, the chain\_hash value MUST be
> (encoded in hex):
> 6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000.

However this wiki entry about Bitcoin's [genesis block](https://en.bitcoin.it/wiki/Genesis_block) has

> GetHash() =
> 0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

Indeed, inputting the latter value into blockchain.info yields [Block 0](https://blockchain.info/block-index/14849/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f), while the former value cannot be found on blockchain.info.

Why does the value `6fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d6190000000000` appear in Lightning Network as "Bitcoin's genesis hash"?

**Tags:** lightning-network, hash, genesis-block, endianness


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## 3 answers

### Answer by username_3 on 2018-04-25. Score: 8 | Accepted answer

They're exactly the same number; one is written in [little endian](https://en.wikipedia.org/wiki/Endianness) notation and the other is big endian. Notice that the bytes (two-hex-digit pairs) are exactly reversed from one to the other.

Block explorers like blockchain.info usually expect big-endian for block hashes. The proof-of-work requirement means that the *most* significant bits have to be zero, so big endian makes it easier to see this.


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### Answer by username_1 on 2018-04-25. Score: 1

It is the same hash but reversed since bitcoin transmits data using little endian format (most significant byte last)


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### Answer by username_2 on 2024-02-29. Score: 0

Also of note, the present [testnet genesis](https://live.blockcypher.com/btc-testnet/block/000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943/):

Big Endian (typical for blockchain explorers):

`000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943`

Little Endian (correct for [block header](https://learnmeabitcoin.com/technical/block-header)):

`43497fd7f826957108f4a30fd9cec3aeba79972084e90ead01ea330900000000`


---

