<p>There are several definitions with overlapping meanings.</p>
<p>The first is perhaps best called <em>extinct</em> blocks. These are blocks that were produced by building on a block that is no longer the active tip of the chain. Some nodes may have considered it to be the best block at some point, but they switched to another chain which does not contain the relevant block anymore. They are valid, verified, and their ancestry up to the genesis block is fully known - they're just not currently 'active'. They are sometimes called stale blocks (typically in the context of mining software realizing it built on old data) or orphan blocks. The latter name originates from the fact that payouts from extinct blocks are denoted as &quot;orphaned&quot; in the reference client (referring to the fact that their coinbase transactions are now orphaned).</p>
<p>However, there also exist real <em>orphan</em> blocks, with orphan in its original meaning of &quot;having no parent&quot;. These are blocks received by a node that does not have its entire ancestry (yet) and thus cannot be validated. Nodes keep such blocks in memory, while asking their peers to fill in the gap of their history. The client does not show these, so when people talk about orphan blocks, they are most likely referring to extinct blocks. Note that since Bitcoin Core v0.10, there are no such orphan blocks anymore, due to a significant change in the download mechanism.</p>
<p>Terminology is confusing here :)</p>

CC BY-SA 3.0
2018-03-19T16:46:17.147Z
Nice explanation Pieter, could you please elaborate on details of current download mechanism that Bitcoin Core uses? I wonder how it solves orphan block problem.
eugenekr
CC BY-SA 3.0
2018-03-19T17:11:17.457Z
@eugenkr The headers are downloaded and validated first, before the client even requests block data. As a result, it will never receive blocks whose parents it doesn't know about.
Pieter Wuille
CC BY-SA 4.0
2019-08-29T18:52:08.997Z
Got to this thread from Twitter. My suggestion is "lonesome block".
Phuoc Do
CC BY-SA 4.0
2021-09-24T00:20:01.167Z
So, to confirm, [this chart at blockchain.com](https://www.blockchain.com/charts/n-orphaned-blocks) is showing what you prefer to call _extinct_ blocks.
davidbak
CC BY-SA 4.0
2012-12-19T23:51:57.557Z
2020-11-25T18:31:32.053Z
2020-11-25T18:31:32.053Z
Pieter Wuille
<p>Orphans are not in the chain (as seen by the processing node) because their parents are missing, stales are not in the chain because they have no children in the chain.</p>

<p>Source: the glossary at bitcoin.org:</p>

<p><a href="https://bitcoin.org/en/glossary/stale-block" rel="noreferrer">stale blocks</a> are:
"Blocks which were successfully mined but which aren’t included on the current best block chain, likely because some other block at the same height had its chain extended first." </p>

<p>and <a href="https://bitcoin.org/en/glossary/orphan-block" rel="noreferrer">orphan blocks</a> are:
"Blocks whose parent block has not been processed by the local node, so they can’t be fully validated yet."</p>

CC BY-SA 3.0
2018-04-02T17:13:52.277Z
"Orphans are not in the chain because they have no parents in the chain" this statement is wrong. orphaned blocks have "parent"-blocks which are part of the blockchain
anion
CC BY-SA 4.0
2018-12-27T17:14:54.107Z
According to https://en.bitcoin.it/wiki/Vocabulary#Orphan_Block: "An orphan block is a block which has no known parent in the currently-longest block chain. Not to be confused with a Stale Block (which has a known parent, but is no longer part of the longest chain)."
Ed Posnak
CC BY-SA 3.0
2018-03-29T23:25:24.000Z
2018-04-03T23:07:49.100Z
2018-04-03T23:07:49.100Z
Ed Posnak
<p>Both answers are quite good and explain well about the <strong>concept</strong> of <strong>orphaned block</strong> (or more precise name according to Pieter Wuilie: <strong>extinct blocks</strong>). I just want to give a specific view for the future readers who could also want to <strong>take a look at the real orphan blocks</strong> in Bitcoin chain, just like me:) </p>

<p>In blockchain.info website, there are some detailed record for those <a href="https://blockchain.info/orphaned-blocks" rel="nofollow noreferrer">orphaned blocks</a>, if you click the block height, even the block header info of those orphaned blocks are there for you, for example an orphaned block <a href="https://blockchain.info/block-height/503949" rel="nofollow noreferrer">503949</a> mined by SlushPool.</p>

<p>It also has a <a href="https://blockchain.info/charts/n-orphaned-blocks" rel="nofollow noreferrer">statistics view of orphaned blocks</a>, I download its csv history and can calculate Bitcoin <strong>orphaned block rate</strong> is about <strong>0.31%</strong> (from 2014/3/18 to 2017/6/14). The statistic excel file is <a href="https://drive.google.com/file/d/1KcxwzBhKC5yStemVTkva56PFfJ57yGfB" rel="nofollow noreferrer">here</a>.</p>

CC BY-SA 4.0
2018-06-02T05:30:28.167Z
2018-06-02T05:41:01.833Z
2018-06-02T05:41:01.833Z
gary
<p><a href="http://btcvsltc.blogspot.co.nz/2012/10/stale-block.html">Stale blocks</a>:</p>

<blockquote>
  <p>At any second, a block may be "solved."  This means that everyone else
  in the world working on that block must stop, and restart their work. 
  Continuing to work after that point is known as working on a "stale
  block" because it is old data, and old transactions.</p>
</blockquote>

<p>My understanding is the term stale is much more commonly applied to shares when mining in a pool, so you're more likely to hear about stale shares than stale blocks. In this case, the pool probably wouldn't even bother checking whether the share actually solved a block or not.</p>

<p><a href="http://blockchain.info/orphaned-blocks">Orphaned blocks</a>:</p>

<blockquote>
  <p>Detached or Orphaned blocks are valid blocks which are not part of the
  main chain. They can occur naturally when two miners produce blocks at
  similar times or they can be caused by an attacker (with enough
  hashing power) attempting to reverse transactions.</p>
</blockquote>

<p>My own understanding is that orphaned blocks are initially accepted by the majority of the network, but are later rejected when proof of a longer blockchain is received that doesn't include that particular block. </p>

<p>This means that a user could see a transaction as having one confirmation and then, if a longer blockchain was received that didn't include the transaction, it could change back to 0 confirmations. </p>

CC BY-SA 4.0
2020-05-01T00:58:51.123Z
As Pieter wrote in his answer, what you are calling an "orphan block" is an extinct block that may contain "orphaned transactions". Actual orphan blocks are blocks that were received by a node before the node received the parent block.
Murch
CC BY-SA 3.0
2012-12-19T21:24:40.237Z
2012-12-19T22:44:47.953Z
2012-12-19T22:44:47.953Z
Highly Irregular
<p>If I understand it right, a stale block is a block for which an earlier confirmation has been found and was accepted by majority of people. This block is considered invalid and is later never used.</p>

<p>But what is a orphaned block. How is it created? How is it verified that it is orphaned and what is done to the orphaned block?</p>

CC BY-SA 4.0
2020-05-01T10:22:01.020Z
Whether or not it has been accepted by a majority is irrelevant to the definition.
Jürgen Strobel
<terminology><orphaned-blocks><stale-block>
What are orphaned and stale blocks?
Salvador Dali
# What are orphaned and stale blocks?

(Asked by: username_0 on 2012-12-19)

If I understand it right, a stale block is a block for which an earlier confirmation has been found and was accepted by majority of people. This block is considered invalid and is later never used.

But what is a orphaned block. How is it created? How is it verified that it is orphaned and what is done to the orphaned block?

**Tags:** terminology, orphaned-blocks, stale-block

> **Comments:**
> **username_1**: Whether or not it has been accepted by a majority is irrelevant to the definition.  

---

## 4 answers

### Answer by username_9 on 2012-12-19. Score: 29 | Accepted answer

[Stale blocks](http://btcvsltc.blogspot.co.nz/2012/10/stale-block.html):

> At any second, a block may be "solved." This means that everyone else
> in the world working on that block must stop, and restart their work.
> Continuing to work after that point is known as working on a "stale
> block" because it is old data, and old transactions.

My understanding is the term stale is much more commonly applied to shares when mining in a pool, so you're more likely to hear about stale shares than stale blocks. In this case, the pool probably wouldn't even bother checking whether the share actually solved a block or not.

[Orphaned blocks](http://blockchain.info/orphaned-blocks):

> Detached or Orphaned blocks are valid blocks which are not part of the
> main chain. They can occur naturally when two miners produce blocks at
> similar times or they can be caused by an attacker (with enough
> hashing power) attempting to reverse transactions.

My own understanding is that orphaned blocks are initially accepted by the majority of the network, but are later rejected when proof of a longer blockchain is received that doesn't include that particular block.

This means that a user could see a transaction as having one confirmation and then, if a longer blockchain was received that didn't include the transaction, it could change back to 0 confirmations.

> **Comments:**
> **username_10**: As username_2 wrote in his answer, what you are calling an "orphan block" is an extinct block that may contain "orphaned transactions". Actual orphan blocks are blocks that were received by a node before the node received the parent block.  

---

### Answer by username_2 on 2012-12-19. Score: 53

There are several definitions with overlapping meanings.

The first is perhaps best called *extinct* blocks. These are blocks that were produced by building on a block that is no longer the active tip of the chain. Some nodes may have considered it to be the best block at some point, but they switched to another chain which does not contain the relevant block anymore. They are valid, verified, and their ancestry up to the genesis block is fully known - they're just not currently 'active'. They are sometimes called stale blocks (typically in the context of mining software realizing it built on old data) or orphan blocks. The latter name originates from the fact that payouts from extinct blocks are denoted as "orphaned" in the reference client (referring to the fact that their coinbase transactions are now orphaned).

However, there also exist real *orphan* blocks, with orphan in its original meaning of "having no parent". These are blocks received by a node that does not have its entire ancestry (yet) and thus cannot be validated. Nodes keep such blocks in memory, while asking their peers to fill in the gap of their history. The client does not show these, so when people talk about orphan blocks, they are most likely referring to extinct blocks. Note that since Bitcoin Core v0.10, there are no such orphan blocks anymore, due to a significant change in the download mechanism.

Terminology is confusing here :)

> **Comments:**
> **username_3**: Nice explanation username_2, could you please elaborate on details of current download mechanism that Bitcoin Core uses? I wonder how it solves orphan block problem.  
> **username_2**: @eugenkr The headers are downloaded and validated first, before the client even requests block data. As a result, it will never receive blocks whose parents it doesn't know about.  
> **username_4**: Got to this thread from Twitter. My suggestion is "lonesome block".  
> **username_5**: So, to confirm, [this chart at blockchain.com](https://www.blockchain.com/charts/n-orphaned-blocks) is showing what you prefer to call _extinct_ blocks.  

---

### Answer by username_6 on 2018-03-29. Score: 5

Orphans are not in the chain (as seen by the processing node) because their parents are missing, stales are not in the chain because they have no children in the chain.

Source: the glossary at bitcoin.org:

[stale blocks](https://bitcoin.org/en/glossary/stale-block) are:
"Blocks which were successfully mined but which aren’t included on the current best block chain, likely because some other block at the same height had its chain extended first."

and [orphan blocks](https://bitcoin.org/en/glossary/orphan-block) are:
"Blocks whose parent block has not been processed by the local node, so they can’t be fully validated yet."

> **Comments:**
> **username_7**: "Orphans are not in the chain because they have no parents in the chain" this statement is wrong. orphaned blocks have "parent"-blocks which are part of the blockchain  
> **username_6**: According to https://en.bitcoin.it/wiki/Vocabulary#Orphan_Block: "An orphan block is a block which has no known parent in the currently-longest block chain. Not to be confused with a Stale Block (which has a known parent, but is no longer part of the longest chain)."  

---

### Answer by username_8 on 2018-06-02. Score: -1

Both answers are quite good and explain well about the **concept** of **orphaned block** (or more precise name according to username_2 Wuilie: **extinct blocks**). I just want to give a specific view for the future readers who could also want to **take a look at the real orphan blocks** in Bitcoin chain, just like me:)

In blockchain.info website, there are some detailed record for those [orphaned blocks](https://blockchain.info/orphaned-blocks), if you click the block height, even the block header info of those orphaned blocks are there for you, for example an orphaned block [503949](https://blockchain.info/block-height/503949) mined by SlushPool.

It also has a [statistics view of orphaned blocks](https://blockchain.info/charts/n-orphaned-blocks), I download its csv history and can calculate Bitcoin **orphaned block rate** is about **0.31%** (from 2014/3/18 to 2017/6/14). The statistic excel file is [here](https://drive.google.com/file/d/1KcxwzBhKC5yStemVTkva56PFfJ57yGfB).


---

