<p>The blockchain is the decentrally maintained append-only log of all
transactions verified on the Bitcoin network. There are multiple websites, so called <em>blockchain explorers</em> that visualize this data on the web.</p>

<p>Indeed all transactions that ever happened on the blockchain are publicly visible, and looking at transactions on such a blockchain explorer let's you discover what transactions moved the same Bitcoin balance before you received it.</p>

<p>While all the transactional information is in the public, the involved parties remain private as they transact under pseudonyms called <em>Bitcoin addresses</em>. We can see time, volume, and involved addresses, but don't learn the individual's private information. </p>

<p>However, through data mining observers may learn that some addresses are under the control of the same entity and might make some guesses about their usage.</p>

CC BY-SA 3.0
2016-07-04T15:28:10.343Z
2016-07-04T15:28:10.343Z
Murch
<p>I am now more familiar with blockchain, and I try to complete this answer. Please don't hesitate to comment.</p>

<p><strong>How to see the blocks?</strong></p>

<p>Here is an <a href="https://blockchain.info/block-height/420032" rel="nofollow">example of block</a>.
We can have a lot of information: time of creation, previous block, next block, etc.</p>

<p><strong>The transactions in one block</strong></p>

<p>It is possible to see all transactions in <a href="https://blockchain.info/block-index/1118347" rel="nofollow">one block</a>. The transactions are represented by several elements: </p>

<ul>
<li>The hash of the transaction</li>
<li>The address of the sender (before the arrow), and I think that multiple addresses are possible because if one decides to send, say, 10 bitcoins to another, he will do it with his portfolio, and it may contains two addresses, with 5 bitcoins each. So in this transaction, the two addresses will be considered as the two sender addresses.</li>
<li>The address of the recipient (after the arrow). Multiple addresses are possible because for several reasons: fees, change, etc.</li>
<li>The number of bitcoins.</li>
</ul>

<p><strong>Details of one transaction</strong></p>

<p>Here is <a href="https://blockchain.info/tx/645989b3d3df37827f4dfe2f75bf2fea1e66e25d2c6c562225c0123d1567f429" rel="nofollow">an example of transaction</a>. We have more detailed information: IP address, transaction fees, etc. (I once saw the transaction detailed page where it is possible to see the previous transaction I think, but I can't find it. Any way, since it is possible to see where one's bitcoin comes from, could you please point out how to see the previous transaction?)</p>

<p><strong>Information about one address</strong></p>

<p>Here is <a href="https://blockchain.info/address/1KyeBoM2XveqjHUQEcK3qgaxnn1bDFMvwU" rel="nofollow">an example of address</a>. We can see the balance, the number of transaction, the total received bitcoins, all transactions details, etc. It is <a href="https://en.bitcoin.it/wiki/Address_reuse" rel="nofollow">recommended to use one address only once</a>. But in practice, it is inevitable to reuse them, for instance, if you use an address to receive the donations. And here are <a href="https://blockchain.info/popular-addresses" rel="nofollow">the most popular addresses</a>. And here are <a href="http://www.bitcoinrichlist.com/top100" rel="nofollow">the top 100 richest addresses</a>.</p>

<p>My initial question was more about privacy. In fact, only adresses are mentionned in these transactions. And we don't know "who" really are behind the adresses. So, there is no privacy issues, unless people put their real name behind the adress. Now that I know more about this <strong>public and shared ledger</strong>, I try to give more information.</p>

CC BY-SA 3.0
2016-07-01T15:40:57.257Z
Correct.  Bitcoin is pseudonymous, so although all transactions are public, you can't always find out who is behind them.  There are ways of doing, this, however, so don't mistake this with complete annonymity.
Jestin
CC BY-SA 3.0
2016-07-04T21:09:28.447Z
In fact, I realised that I didn't understand that accounts are different from adresses. Are all adresses publicly linked to accounts ?
John Smith
CC BY-SA 3.0
2016-07-04T22:28:54.070Z
There's no such thing as an "account"in Bitcoin, which is why you may be confused.  There are only addresses.  One wallet controls many addresses, and usually uses a completely new one with every transaction.
Jestin
CC BY-SA 3.0
2016-07-10T12:14:06.530Z
@Jestin: There are no accounts in the Bitcoin *protocol*, but there are definitely accounts in the Bitcoin *software*, and there have been since very early versions of the Bitcoin Core software (then called simply "Bitcoin"). https://en.bitcoin.it/wiki/Help:Accounts_explained
Meni Rosenfeld
CC BY-SA 3.0
2016-07-10T12:15:50.350Z
@XRSC: Accounts are internal bookkeeping mechanisms of Bitcoin wallet software. There is no public information about accounts whatsoever, and they are irrelevant for the protocol.
Meni Rosenfeld
CC BY-SA 3.0
2016-07-01T15:29:31.330Z
2016-07-09T23:40:18.687Z
2016-07-09T23:40:18.687Z
John Smith
<p>The blockchain is a shared public ledger for Bitcoin. What does that mean exactly? Is it possible to see, publicly, all transactions? For every bitcoin a person owns, is he able to see all the historical transactions? If so, there should be privacy issues, no? If he can't, who can?</p>

CC BY-SA 3.0
2016-07-01T13:17:59.930Z
I would tell you to ask each of these questions individually, but most of them have already been asked and have good answers.  I think you are probably best off reading some more basic documentation first, and then asking for clarifications when needed.  Try starting here:  https://bitcoin.org/en/how-it-works or here:  https://simple.wikipedia.org/wiki/Bitcoin
Jestin
CC BY-SA 3.0
2016-07-01T15:25:43.220Z
Thank you for your comment, I deleted questions that are not linked to the title.
John Smith
CC BY-SA 3.0
2016-07-04T15:20:28.077Z
related: [Can someone explain how the Bitcoin Blockchain works?](http://bitcoin.stackexchange.com/q/12427/5406)
Murch
<transactions><blockchain><privacy>
Since the blockchain is public, how can we see it?
John Smith
# Since the blockchain is public, how can we see it?

(Asked by: username_0 on 2016-07-01)

The blockchain is a shared public ledger for Bitcoin. What does that mean exactly? Is it possible to see, publicly, all transactions? For every bitcoin a person owns, is he able to see all the historical transactions? If so, there should be privacy issues, no? If he can't, who can?

**Tags:** transactions, blockchain, privacy

> **Comments:**
> **username_1**: I would tell you to ask each of these questions individually, but most of them have already been asked and have good answers.  I think you are probably best off reading some more basic documentation first, and then asking for clarifications when needed.  Try starting here:  https://bitcoin.org/en/how-it-works or here:  https://simple.wikipedia.org/wiki/Bitcoin  
> **username_0**: Thank you for your comment, I deleted questions that are not linked to the title.  
> **username_2**: related: [Can someone explain how the Bitcoin Blockchain works?](http://bitcoin.stackexchange.com/q/12427/5406)  

---

## 2 answers

### Answer by username_2 on 2016-07-04. Score: 4

The blockchain is the decentrally maintained append-only log of all
transactions verified on the Bitcoin network. There are multiple websites, so called *blockchain explorers* that visualize this data on the web.

Indeed all transactions that ever happened on the blockchain are publicly visible, and looking at transactions on such a blockchain explorer let's you discover what transactions moved the same Bitcoin balance before you received it.

While all the transactional information is in the public, the involved parties remain private as they transact under pseudonyms called *Bitcoin addresses*. We can see time, volume, and involved addresses, but don't learn the individual's private information.

However, through data mining observers may learn that some addresses are under the control of the same entity and might make some guesses about their usage.


---

### Answer by username_0 on 2016-07-01. Score: 1

I am now more familiar with blockchain, and I try to complete this answer. Please don't hesitate to comment.

**How to see the blocks?**

Here is an [example of block](https://blockchain.info/block-height/420032).
We can have a lot of information: time of creation, previous block, next block, etc.

**The transactions in one block**

It is possible to see all transactions in [one block](https://blockchain.info/block-index/1118347). The transactions are represented by several elements:

* The hash of the transaction
* The address of the sender (before the arrow), and I think that multiple addresses are possible because if one decides to send, say, 10 bitcoins to another, he will do it with his portfolio, and it may contains two addresses, with 5 bitcoins each. So in this transaction, the two addresses will be considered as the two sender addresses.
* The address of the recipient (after the arrow). Multiple addresses are possible because for several reasons: fees, change, etc.
* The number of bitcoins.

**Details of one transaction**

Here is [an example of transaction](https://blockchain.info/tx/645989b3d3df37827f4dfe2f75bf2fea1e66e25d2c6c562225c0123d1567f429). We have more detailed information: IP address, transaction fees, etc. (I once saw the transaction detailed page where it is possible to see the previous transaction I think, but I can't find it. Any way, since it is possible to see where one's bitcoin comes from, could you please point out how to see the previous transaction?)

**Information about one address**

Here is [an example of address](https://blockchain.info/address/1KyeBoM2XveqjHUQEcK3qgaxnn1bDFMvwU). We can see the balance, the number of transaction, the total received bitcoins, all transactions details, etc. It is [recommended to use one address only once](https://en.bitcoin.it/wiki/Address_reuse). But in practice, it is inevitable to reuse them, for instance, if you use an address to receive the donations. And here are [the most popular addresses](https://blockchain.info/popular-addresses). And here are [the top 100 richest addresses](http://www.bitcoinrichlist.com/top100).

My initial question was more about privacy. In fact, only adresses are mentionned in these transactions. And we don't know "who" really are behind the adresses. So, there is no privacy issues, unless people put their real name behind the adress. Now that I know more about this **public and shared ledger**, I try to give more information.

> **Comments:**
> **username_1**: Correct.  Bitcoin is pseudonymous, so although all transactions are public, you can't always find out who is behind them.  There are ways of doing, this, however, so don't mistake this with complete annonymity.  
> **username_0**: In fact, I realised that I didn't understand that accounts are different from adresses. Are all adresses publicly linked to accounts ?  
> **username_1**: There's no such thing as an "account"in Bitcoin, which is why you may be confused.  There are only addresses.  One wallet controls many addresses, and usually uses a completely new one with every transaction.  
> **username_3**: @username_1: There are no accounts in the Bitcoin *protocol*, but there are definitely accounts in the Bitcoin *software*, and there have been since very early versions of the Bitcoin Core software (then called simply "Bitcoin"). https://en.bitcoin.it/wiki/Help:Accounts_explained  
> **username_3**: @XRSC: Accounts are internal bookkeeping mechanisms of Bitcoin wallet software. There is no public information about accounts whatsoever, and they are irrelevant for the protocol.  

---

