<p>Bitcoin's state gets synchronized by everyone downloading the blockchain and applying all transactions in the correct order. Earlier versions of Bitcoin would just download block for block until they were caught up. Nowadays, Bitcoin first synchronizes only the block headers which are 80 bytes each and allow the node to pre-filter orphaned blocks and dead sidechains, before downloading all the corresponding blockchain data.</p>
<p>When your computer got shut down, likely some of your node's blockchain state got mixed up, so it's rebuilding the chainstate database, first headers, then blocks.</p>
<hr />
<p>Related:</p>
<ul>
<li><a href="https://bitcoin.stackexchange.com/q/4461/5406">Why is downloading blocks taking longer and longer?</a></li>
<li><a href="https://bitcoin.stackexchange.com/q/9277/5406">How to increase the speed of synchronisation?</a></li>
</ul>

CC BY-SA 4.0
2018-09-22T16:32:43.433Z
2024-01-27T19:32:25.687Z
2024-01-27T19:32:25.687Z
Murch
<p>My system got shut down while I was syncronising. Please help me, it's showing "Unknown. Syncing Headers" and estimated time is unknown.  What is happening here? </p>

<p><a href="https://i.sstatic.net/hrzGL.jpg" rel="noreferrer"><img src="https://i.sstatic.net/hrzGL.jpg" alt="enter image description here"></a> </p>

<synchronization>
My system is syncing headers, what does that mean?
Olamilekan
# My system is syncing headers, what does that mean?

(Asked by: username_0 on 2018-09-22)

My system got shut down while I was syncronising. Please help me, it's showing "Unknown. Syncing Headers" and estimated time is unknown. What is happening here?

[![enter image description here](https://i.sstatic.net/hrzGL.jpg)](https://i.sstatic.net/hrzGL.jpg)

**Tags:** synchronization


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## 1 answers

### Answer by username_1 on 2018-09-22. Score: 4

Bitcoin's state gets synchronized by everyone downloading the blockchain and applying all transactions in the correct order. Earlier versions of Bitcoin would just download block for block until they were caught up. Nowadays, Bitcoin first synchronizes only the block headers which are 80 bytes each and allow the node to pre-filter orphaned blocks and dead sidechains, before downloading all the corresponding blockchain data.

When your computer got shut down, likely some of your node's blockchain state got mixed up, so it's rebuilding the chainstate database, first headers, then blocks.

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Related:

* [Why is downloading blocks taking longer and longer?](https://bitcoin.stackexchange.com/q/4461/5406)
* [How to increase the speed of synchronisation?](https://bitcoin.stackexchange.com/q/9277/5406)


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