<p>Bitcoin is trustless, so you need to validate the transaction yourself. The miner are rewarded for protecting the network by working on special hash. A miner that would release a block with an invalid transaction would be rejected by all nodes and would not work... because everyone is validating everything.</p>

<p>The whole blockchain is not required to validate, in fact you need only unspent outputs. Right now there is no way to get that beside download the whole blockchain.</p>

CC BY-SA 3.0
2015-07-11T02:20:16.930Z
2017-11-10T17:51:21.070Z
2017-11-10T17:51:21.070Z
Zyo
<p>The miners <em>create</em> the blockchain, most of them don't keep track of it directly, just the mining pool operators, and (if there still are some) the  solo miners.<br>
Actually, as the recent blockchain fork shows, <a href="https://bitcoin.stackexchange.com/a/38439/5406">not even all mining pool operators are reliably checking the blockchain</a>. </p>

<p>So, ultimately, the checking is mostly done by full nodes, which also provide data to SPV wallets. If you are running Bitcoin-Core, you are part of those that provide this verification.</p>

<p>If that's not what you are interested in signing up for, you might be happier with a lightweight wallet.</p>

CC BY-SA 3.0
2015-07-21T18:18:17.070Z
2015-07-22T00:31:49.143Z
2017-04-13T12:47:36.647Z
Murch
<p>Certainly miners, and many other users, keep track of the block chain.</p>

<p>But if you don't download and verify the block chain yourself, what will you do when you want to know whether a transaction is valid?  You could ask a miner, but what if they decide to lie to you?  You would have to trust them to tell you the truth.</p>

<p>Part of the Bitcoin security model is that you don't have to trust anybody.  When you verify the block chain for yourself, nobody can trick you into believing that an invalid transaction is valid, or vice versa.</p>

CC BY-SA 3.0
2015-07-11T02:51:22.790Z
Ok great, and maybe I don't understand what mining is exactly, but me verifying the block chain is not mining?  If I understand correctly, I am not  helping verifying the block chain, but rather am getting the blockchain that has been verified by the entire BTC network?
Hurricane Development
CC BY-SA 3.0
2015-07-11T03:26:27.347Z
No, you're not mining.  It's not really accurate to say that the purpose of mining is "verifying" the block chain, i.e. making sure all transactions are valid, because as we see, everyone can do that for themselves.  The purpose of mining is to ensure that valid transactions cannot later be undone (made invalid).  For more information, start with http://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining
Nate Eldredge
CC BY-SA 3.0
2015-07-11T01:08:19.083Z
2015-07-11T01:08:19.083Z
Nate Eldredge
<p>I understand that the blockchain is what keeps track of who has what coins and makes sure that everything is correct and secure, but why do I have to download it?  Isn't that where the miners come in?  Don't they keep track of the blockchain?</p>

<blockchain><bitcoin-core>
Why does bitcoin core need to download the blockchain
Hurricane Development
# Why does bitcoin core need to download the blockchain

(Asked by: username_0 on 2015-07-10)

I understand that the blockchain is what keeps track of who has what coins and makes sure that everything is correct and secure, but why do I have to download it? Isn't that where the miners come in? Don't they keep track of the blockchain?

**Tags:** blockchain, bitcoin-core


---

## 3 answers

### Answer by username_3 on 2015-07-11. Score: 11 | Accepted answer

Certainly miners, and many other users, keep track of the block chain.

But if you don't download and verify the block chain yourself, what will you do when you want to know whether a transaction is valid? You could ask a miner, but what if they decide to lie to you? You would have to trust them to tell you the truth.

Part of the Bitcoin security model is that you don't have to trust anybody. When you verify the block chain for yourself, nobody can trick you into believing that an invalid transaction is valid, or vice versa.

> **Comments:**
> **username_0**: Ok great, and maybe I don't understand what mining is exactly, but me verifying the block chain is not mining?  If I understand correctly, I am not  helping verifying the block chain, but rather am getting the blockchain that has been verified by the entire BTC network?  
> **username_3**: No, you're not mining.  It's not really accurate to say that the purpose of mining is "verifying" the block chain, i.e. making sure all transactions are valid, because as we see, everyone can do that for themselves.  The purpose of mining is to ensure that valid transactions cannot later be undone (made invalid).  For more information, start with http://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining  

---

### Answer by username_1 on 2015-07-11. Score: 2

Bitcoin is trustless, so you need to validate the transaction yourself. The miner are rewarded for protecting the network by working on special hash. A miner that would release a block with an invalid transaction would be rejected by all nodes and would not work... because everyone is validating everything.

The whole blockchain is not required to validate, in fact you need only unspent outputs. Right now there is no way to get that beside download the whole blockchain.


---

### Answer by username_2 on 2015-07-21. Score: 1

The miners *create* the blockchain, most of them don't keep track of it directly, just the mining pool operators, and (if there still are some) the solo miners.  
Actually, as the recent blockchain fork shows, [not even all mining pool operators are reliably checking the blockchain](https://bitcoin.stackexchange.com/a/38439/5406).

So, ultimately, the checking is mostly done by full nodes, which also provide data to SPV wallets. If you are running Bitcoin-Core, you are part of those that provide this verification.

If that's not what you are interested in signing up for, you might be happier with a lightweight wallet.


---

