<p>The TXID is the hash of the transaction.</p>

CC BY-SA 3.0
2018-03-15T15:39:17.413Z
2018-03-15T15:39:17.413Z
Claris
<p>TXID is the double sha256 hash of the signed transaction, used to uniquely identify a particular transaction.</p>
<p>When you create/sign a transaction that hash will be generated with your transaction.</p>

CC BY-SA 3.0
2018-03-15T20:28:08.560Z
So it's the digital signature? Is there a comprehensive website that I can use to read up on bitcoin? From a programmers point of view.
Kyle Graham
CC BY-SA 3.0
2018-03-15T20:29:36.017Z
Yeah, There's a book called Mastering Bitcoin by Andreas Antonopoulos , Best book ever.
Tailer
CC BY-SA 4.0
2020-12-27T14:40:06.867Z
If TxId is the hash of the transaction data, how it is made unique to guard against fraudulent duplicate transactions (including timestamp)?
Hiranmay Ghosh
CC BY-SA 4.0
2020-12-27T17:02:18.120Z
@HiranmayGhosh: The output of cryptographic hash functions is collision resistant and 2^256 is a huge space of numbers.
Murch
CC BY-SA 4.0
2020-12-29T12:19:36.893Z
It is the *double* sha256.
Antoine Poinsot
CC BY-SA 4.0
2018-03-15T16:33:12.150Z
2020-12-29T12:21:37.513Z
2020-12-29T12:21:37.513Z
Tailer
<p>In the blockchain, every transaction has a transactionId where does this come from?</p>

<transactions><bitcoin-core>
How is the transactionId generated?
Kyle Graham
# How is the transactionId generated?

(Asked by: username_0 on 2018-03-15)

In the blockchain, every transaction has a transactionId where does this come from?

**Tags:** transactions, bitcoin-core


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## 2 answers

### Answer by username_2 on 2018-03-15. Score: 5 | Accepted answer

TXID is the double sha256 hash of the signed transaction, used to uniquely identify a particular transaction.

When you create/sign a transaction that hash will be generated with your transaction.

> **Comments:**
> **username_0**: So it's the digital signature? Is there a comprehensive website that I can use to read up on bitcoin? From a programmers point of view.  
> **username_2**: Yeah, There's a book called Mastering Bitcoin by Andreas Antonopoulos , Best book ever.  
> **username_3**: If TxId is the hash of the transaction data, how it is made unique to guard against fraudulent duplicate transactions (including timestamp)?  
> **username_4**: @HiranmayGhosh: The output of cryptographic hash functions is collision resistant and 2^256 is a huge space of numbers.  
> **username_5**: It is the *double* sha256.  

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### Answer by username_1 on 2018-03-15. Score: 0

The TXID is the hash of the transaction.


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