<p>That has to be a parsing error from blockchain.com side. It would be indeed a double-spend and therefore block 525891 would have been invalid.</p>

<p>If you check other explorers (e.g. <a href="https://blockstream.info/block/0000000000000000001a1be9200a8f6921c77e3f3f59c812d39999da76f87bd4" rel="nofollow noreferrer">blockstream</a> or <a href="https://live.blockcypher.com/btc/block/0000000000000000001a1be9200a8f6921c77e3f3f59c812d39999da76f87bd4/" rel="nofollow noreferrer">blockcypher</a>) you'll see how they had only included it in block 525891.</p>

<p>Personally I find blockchain.info's explorer not to be too reliable.</p>

CC BY-SA 4.0
2019-09-26T08:53:32.783Z
Actually I found out about the double spend using my own parser that returns an error because the same UTXO is used twice. I am parsing the blocks from my own full node.
Kevin P
CC BY-SA 4.0
2019-09-26T08:56:36.710Z
And it agrees with blockchain info, the UTXO is created in block 525859 and spent in blocks 525890 and 525891
Kevin P
CC BY-SA 4.0
2019-09-26T08:32:35.137Z
2019-09-26T08:32:35.137Z
sr_gi
<p>Occasionally, minor alternate chains emerge if multiple blocks are found for a given blockheight. Usually, these alternate chains only last for a single blocked, and are quickly dropped once another block has been found, allowing one chain to become longer (and thus have more work).</p>

<p>More rarely, these chains might last for a couple of blocks.</p>

<p>Block <a href="https://www.blockchain.com/btc/block-index/1704047" rel="noreferrer">525890</a> for this tx is not part of the main Bitcoin chain, and thus the tx was unspent when block <a href="https://www.blockchain.com/btc/block-index/1704049" rel="noreferrer">525891</a> was processed.</p>

<pre><code>525889 ------ 525890 ------ 525891*
      \------ 525890*
</code></pre>

<p>The blocks marked with * contain the transaction in question here. As you can see, they occur on separate, parallel chains. Of these, only the chain extending 525891 survived, resulting in the version of block 525890 containing the transaction being dropped.</p>

CC BY-SA 4.0
2019-09-26T10:40:54.367Z
You must be right. I doubled checked and my parser is using the same extinct block as blockchain.info. My block index must be wrong I will have to double check this.
Kevin P
CC BY-SA 4.0
2019-09-26T09:16:59.463Z
2019-09-26T09:16:59.463Z
Raghav Sood
<p><a href="https://www.blockchain.com/btc/tx/a7bacce00e5df85d3547a3f83ac10c65eec30f715c1d77d8d4a7bc17fd470965" rel="nofollow noreferrer">https://www.blockchain.com/btc/tx/a7bacce00e5df85d3547a3f83ac10c65eec30f715c1d77d8d4a7bc17fd470965</a></p>

<p>How is it possible that a single tx is included in two different blocks?</p>

<p>Isn't it considered double spending?</p>

<transactions><doublespend>
Single tx included in two different blocks
Kevin P
# Single tx included in two different blocks

(Asked by: username_0 on 2019-09-26)

<https://www.blockchain.com/btc/tx/a7bacce00e5df85d3547a3f83ac10c65eec30f715c1d77d8d4a7bc17fd470965>

How is it possible that a single tx is included in two different blocks?

Isn't it considered double spending?

**Tags:** transactions, doublespend


---

## 2 answers

### Answer by username_2 on 2019-09-26. Score: 6 | Accepted answer

Occasionally, minor alternate chains emerge if multiple blocks are found for a given blockheight. Usually, these alternate chains only last for a single blocked, and are quickly dropped once another block has been found, allowing one chain to become longer (and thus have more work).
More rarely, these chains might last for a couple of blocks.
Block 525890 for this tx is not part of the main Bitcoin chain, and thus the tx was unspent when block 525891 was processed.
525889 ------ 525890 ------ 525891*
      \------ 525890*

The blocks marked with * contain the transaction in question here. As you can see, they occur on separate, parallel chains. Of these, only the chain extending 525891 survived, resulting in the version of block 525890 containing the transaction being dropped.

> **Comments:**
> **username_0**: You must be right. I doubled checked and my parser is using the same extinct block as blockchain.info. My block index must be wrong I will have to double check this.  

---

### Answer by username_1 on 2019-09-26. Score: 2

That has to be a parsing error from blockchain.com side. It would be indeed a double-spend and therefore block 525891 would have been invalid.

If you check other explorers (e.g. [blockstream](https://blockstream.info/block/0000000000000000001a1be9200a8f6921c77e3f3f59c812d39999da76f87bd4) or [blockcypher](https://live.blockcypher.com/btc/block/0000000000000000001a1be9200a8f6921c77e3f3f59c812d39999da76f87bd4/)) you'll see how they had only included it in block 525891.

Personally I find blockchain.info's explorer not to be too reliable.

> **Comments:**
> **username_0**: Actually I found out about the double spend using my own parser that returns an error because the same UTXO is used twice. I am parsing the blocks from my own full node.  
> **username_0**: And it agrees with blockchain info, the UTXO is created in block 525859 and spent in blocks 525890 and 525891  

---

