<p>Sequence is part of any input, before segwit as well. <code>feffffff</code> is the hexadecimal number 0xfffffffe because the bytes need to be reversed. This sequence number, as per <a href="https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki" rel="nofollow noreferrer">BIP 125</a>, is because:</p>

<blockquote>
  <p>Wallets that don't want to signal replaceability should use either a max sequence number (0xffffffff) or a sequence number of (0xffffffff-1) when then also want to use locktime;</p>
</blockquote>

<p>So this sequence number uses the locktime but does not signal replaceability</p>

<p>If instead you used 0xffffffff, the sequence number would have no effect on the transaction.</p>

<p>If you don't know what locktime is, check out this question: <a href="https://bitcoin.stackexchange.com/questions/43067/what-is-bitcoins-locktime-feature-exactly-how-can-it-be-used">What is Bitcoin&#39;s locktime feature exactly? How can it be used?</a></p>

CC BY-SA 3.0
2017-08-18T21:01:41.353Z
So, "What [actually] happens if its 'feffffff' instead of 'ffffffff'?"  "Does it help anything, does it hurt anything?  Am I just fine using just 'ffffffff' instead of 'feffffff'?".  and what does "locktime" mean?
Mine
CC BY-SA 3.0
2017-08-18T21:20:54.613Z
Use feffffff if you want to use the locktime functionality in your transaction. Asking what locktime is is a distinct question, should not be a comment https://bitcoin.stackexchange.com/questions/43067/what-is-bitcoins-locktime-feature-exactly-how-can-it-be-used
meshcollider
CC BY-SA 3.0
2017-08-18T22:48:54.233Z
I would put forth that that is not necessarily the case.  Thank you for the update to your answer and the link.
Mine
CC BY-SA 3.0
2017-08-17T20:38:04.883Z
2017-08-18T21:22:51.743Z
2017-08-18T21:22:51.743Z
meshcollider
<p>On the <a href="https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki#p2sh-p2wpkh" rel="nofollow noreferrer">segwit page</a> there is a reference that the "feffffff" is the "sequence".  What does the "sequence" represent in relation to what?  Does it always have to be "feffffff"?  What happens if it's "feffffff" instead of "ffffffff"?  Does it help anything, does it hurt anything?  Am I just fine using just "ffffffff" instead of "feffffff" What other options are there and what do they mean?</p>

<transactions><raw-transaction><sequence>
What is the "sequence" and its details as referenced for the segwit application?
Mine
# What is the "sequence" and its details as referenced for the segwit application?

(Asked by: username_0 on 2017-08-17)

On the [segwit page](https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki#p2sh-p2wpkh) there is a reference that the "feffffff" is the "sequence". What does the "sequence" represent in relation to what? Does it always have to be "feffffff"? What happens if it's "feffffff" instead of "ffffffff"? Does it help anything, does it hurt anything? Am I just fine using just "ffffffff" instead of "feffffff" What other options are there and what do they mean?

**Tags:** transactions, raw-transaction, sequence


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## 1 answers

### Answer by username_1 on 2017-08-17. Score: 5 | Accepted answer

Sequence is part of any input, before segwit as well. `feffffff` is the hexadecimal number 0xfffffffe because the bytes need to be reversed. This sequence number, as per [BIP 125](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki), is because:

> Wallets that don't want to signal replaceability should use either a max sequence number (0xffffffff) or a sequence number of (0xffffffff-1) when then also want to use locktime;

So this sequence number uses the locktime but does not signal replaceability

If instead you used 0xffffffff, the sequence number would have no effect on the transaction.

If you don't know what locktime is, check out this question: [What is Bitcoin's locktime feature exactly? How can it be used?](https://bitcoin.stackexchange.com/questions/43067/what-is-bitcoins-locktime-feature-exactly-how-can-it-be-used)

> **Comments:**
> **username_0**: So, "What [actually] happens if its 'feffffff' instead of 'ffffffff'?"  "Does it help anything, does it hurt anything?  Am I just fine using just 'ffffffff' instead of 'feffffff'?".  and what does "locktime" mean?  
> **username_1**: Use feffffff if you want to use the locktime functionality in your transaction. Asking what locktime is is a distinct question, should not be a comment https://bitcoin.stackexchange.com/questions/43067/what-is-bitcoins-locktime-feature-exactly-how-can-it-be-used  
> **username_0**: I would put forth that that is not necessarily the case.  Thank you for the update to your answer and the link.  

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