<blockquote>
  <p>Q: does this "desired pattern" always have the same leading zeros?</p>
</blockquote>

<p>No.</p>

<blockquote>
  <p>Or does that change now and then?</p>
</blockquote>

<p>It changes every ~14 days (2016 blocks). The change depends on the hashing power of the bitcoin network at that moment. The new required hash needs to have that many leading zeros so that it takes ~10 minutes to find that hash.</p>

<blockquote>
  <p>Q: If it changes now and then, what triggers this?</p>
</blockquote>

<p>An algorithm triggers it. It's built into the bitcoin protocol. Every 2016 blocks the difficulty of finding a new block is recalculated.</p>

CC BY-SA 3.0
2016-02-01T13:25:38.997Z
OK, so the change of the desired pattern is directly linked with the mining difficulty?
mvanderbilt
CC BY-SA 3.0
2016-02-01T15:19:22.457Z
Yes. See [here](https://en.bitcoin.it/wiki/Difficulty) and more specifically [here](https://en.bitcoin.it/wiki/Difficulty#What_network_hash_rate_results_in_a_given_difficulty.3F) for details.
karask
CC BY-SA 3.0
2016-02-01T13:07:29.887Z
2016-02-01T14:35:49.557Z
2016-02-01T14:35:49.557Z
karask
<p>If I understood it well, miners collect transactions in temporary files on which they apply a cryptographic function. The result will be reviewed against a desired pattern.</p>

<p>Does this "desired pattern" always have the same leading zeros? Or does that change now and then?<br>
If it changes now and then, what triggers this?</p>

CC BY-SA 3.0
2016-02-01T14:43:11.323Z
possible duplicate of [How is difficulty calculated?](http://bitcoin.stackexchange.com/q/5838/5406)
Murch
<difficulty><mining-theory><block-header>
Do the leading zeros in the desired hash pattern for mining change?
mvanderbilt
# Do the leading zeros in the desired hash pattern for mining change?

(Asked by: username_0 on 2016-02-01)

If I understood it well, miners collect transactions in temporary files on which they apply a cryptographic function. The result will be reviewed against a desired pattern.

Does this "desired pattern" always have the same leading zeros? Or does that change now and then?  
If it changes now and then, what triggers this?

**Tags:** difficulty, mining-theory, block-header

> **Comments:**
> **username_1**: possible duplicate of [How is difficulty calculated?](http://bitcoin.stackexchange.com/q/5838/5406)  

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## 1 answers

### Answer by username_2 on 2016-02-01. Score: 2 | Accepted answer

> Q: does this "desired pattern" always have the same leading zeros?

No.

> Or does that change now and then?

It changes every ~14 days (2016 blocks). The change depends on the hashing power of the bitcoin network at that moment. The new required hash needs to have that many leading zeros so that it takes ~10 minutes to find that hash.

> Q: If it changes now and then, what triggers this?

An algorithm triggers it. It's built into the bitcoin protocol. Every 2016 blocks the difficulty of finding a new block is recalculated.

> **Comments:**
> **username_0**: OK, so the change of the desired pattern is directly linked with the mining difficulty?  
> **username_2**: Yes. See [here](https://en.bitcoin.it/wiki/Difficulty) and more specifically [here](https://en.bitcoin.it/wiki/Difficulty#What_network_hash_rate_results_in_a_given_difficulty.3F) for details.  

---

