<p>You may not have been able to find them because they're encoded as separate bytes. You can find them in <code>src/chainparams.cpp</code>, currently on <a href="https://github.com/bitcoin/bitcoin/blob/6d859cbd794a36ed1c0c72324a4ec54d029b3d3b/src/chainparams.cpp#L102" rel="nofollow noreferrer">lines 102–105</a>. I found the code section after noticing that the Bitcoin Developer Guide <a href="https://btcinformation.org/en/developer-reference#constants-and-defaults" rel="nofollow noreferrer">referred</a> to the value as &quot;Start String&quot; and searching the code base for that term.</p>
<p>This is the relevant section of code.</p>
<pre><code>    /**
     * The message start string is designed to be unlikely to occur in normal data.
     * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
     * a large 32-bit integer with any alignment.
     */
    pchMessageStart[0] = 0xf9;
    pchMessageStart[1] = 0xbe;
    pchMessageStart[2] = 0xb4;
    pchMessageStart[3] = 0xd9;
</code></pre>

CC BY-SA 4.0
2022-01-23T15:30:22.917Z
OMG, I went code blind and was fixated on a single assignment. 

It’s right bloody there!!!
LeosSire
CC BY-SA 4.0
2022-01-23T12:42:53.573Z
2022-01-23T12:56:18.887Z
2022-01-23T12:56:18.887Z
Murch
<p>This has been bugging me. I’d have expected the magic number to be in the <code>chainParams.cpp</code> but I can’t find it.</p>
<p>Where is bitcoin's magic number stored in the source code?</p>

<bitcoin-core-development><peer-discovery>
Where is the magic number stated?
LeosSire
# Where is the magic number stated?

(Asked by: username_0 on 2022-01-23)

This has been bugging me. I’d have expected the magic number to be in the `chainParams.cpp` but I can’t find it.

Where is bitcoin's magic number stored in the source code?

**Tags:** bitcoin-core-development, peer-discovery


---

## 1 answers

### Answer by username_1 on 2022-01-23. Score: 1 | Accepted answer

You may not have been able to find them because they're encoded as separate bytes. You can find them in `src/chainparams.cpp`, currently on [lines 102–105](https://github.com/bitcoin/bitcoin/blob/6d859cbd794a36ed1c0c72324a4ec54d029b3d3b/src/chainparams.cpp#L102). I found the code section after noticing that the Bitcoin Developer Guide [referred](https://btcinformation.org/en/developer-reference#constants-and-defaults) to the value as "Start String" and searching the code base for that term.

This is the relevant section of code.

```
    /**
     * The message start string is designed to be unlikely to occur in normal data.
     * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
     * a large 32-bit integer with any alignment.
     */
    pchMessageStart[0] = 0xf9;
    pchMessageStart[1] = 0xbe;
    pchMessageStart[2] = 0xb4;
    pchMessageStart[3] = 0xd9;

```

> **Comments:**
> **username_0**: OMG, I went code blind and was fixated on a single assignment.   It’s right bloody there!!!  

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