<p>It is because in the developer guide they are referring to the <a href="https://bitcoin.org/en/glossary/outpoint" rel="nofollow noreferrer">outpoint</a>, not the output. The outpoint is a data structure used to reference a particular output that consists of:</p>
<pre><code>outpoint = txid (32 bytes) + output index (4 bytes)
</code></pre>

CC BY-SA 4.0
2017-02-23T23:00:21.133Z
2024-08-29T13:27:01.870Z
2024-08-29T13:27:01.870Z
sr_gi
<p>I am reading the bitcoin developer reference and having a look on the transaction input structure. If you have a look at <a href="https://bitcoin.org/en/developer-reference#raw-transaction-format" rel="nofollow noreferrer">raw-transaction-format</a> it says that the previous output has 36 bytes. I am confused, because I read in 'Mastering Bitcoin Book' and this wiki page (<a href="https://en.bitcoin.it/wiki/Transaction" rel="nofollow noreferrer">https://en.bitcoin.it/wiki/Transaction</a>) that the size is 32 bytes.</p>
<p>Is this a mistake in the reference or is it something new which did not propagate to the other sites?</p>

<transactions><transaction-input>
What is the transaction input’s previous hash size?
Donut
# What is the transaction input’s previous hash size?

(Asked by: username_0 on 2017-02-23)

I am reading the bitcoin developer reference and having a look on the transaction input structure. If you have a look at [raw-transaction-format](https://bitcoin.org/en/developer-reference#raw-transaction-format) it says that the previous output has 36 bytes. I am confused, because I read in 'Mastering Bitcoin Book' and this wiki page (<https://en.bitcoin.it/wiki/Transaction>) that the size is 32 bytes.

Is this a mistake in the reference or is it something new which did not propagate to the other sites?

**Tags:** transactions, transaction-input


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## 1 answers

### Answer by username_1 on 2017-02-23. Score: 1 | Accepted answer

It is because in the developer guide they are referring to the [outpoint](https://bitcoin.org/en/glossary/outpoint), not the output. The outpoint is a data structure used to reference a particular output that consists of:

```
outpoint = txid (32 bytes) + output index (4 bytes)

```


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