<p>There are a few different factors for the synchronization time:</p>

<ul>
<li>You're not only downloading data, but the data is also being validated. There is a lot of I/O going on. Disk speed is a significant factor.</li>
<li>The earlier blocks are much smaller than the later blocks. Validation time roughly scales linearly with the data size.</li>
<li>Complexity of transactions may have increased over time, transactions with more inputs take significantly more time to validate.</li>
<li>The UTXO database grows larger as you parse the blockchain, and every input for every transaction has to be looked up in the UTXO database.</li>
</ul>

CC BY-SA 3.0
2016-07-02T12:43:06.863Z
2016-07-02T12:43:06.863Z
Murch
<p>I have been downloading the blockchain to a new client and it has been at it now for almost a week. One thing I notice is that as it is getting close to the end, it is slowing down a lot.</p>

<p>For example, it just downloaded 93 blocks in 488 seconds or 1 block per 5.25 seconds. If the entire block chain had downloaded at this speed then it would take: 418950 x 5.25 = 2,199,488 seconds or 25 days. Since, it has taken less than a week to do it, the older blocks must have downloaded faster.</p>

<p>What is the explanation for this?</p>

CC BY-SA 3.0
2016-07-02T12:43:26.850Z
related: [Why is downloading blocks taking longer and longer?](http://bitcoin.stackexchange.com/q/4461/5406)
Murch
<blockchain><synchronization>
Takes longer to download newer blocks?
Harry Pillsbury
# Takes longer to download newer blocks?

(Asked by: username_0 on 2016-07-02)

I have been downloading the blockchain to a new client and it has been at it now for almost a week. One thing I notice is that as it is getting close to the end, it is slowing down a lot.

For example, it just downloaded 93 blocks in 488 seconds or 1 block per 5.25 seconds. If the entire block chain had downloaded at this speed then it would take: 418950 x 5.25 = 2,199,488 seconds or 25 days. Since, it has taken less than a week to do it, the older blocks must have downloaded faster.

What is the explanation for this?

**Tags:** blockchain, synchronization

> **Comments:**
> **username_1**: related: [Why is downloading blocks taking longer and longer?](http://bitcoin.stackexchange.com/q/4461/5406)  

---

## 1 answers

### Answer by username_1 on 2016-07-02. Score: 1

There are a few different factors for the synchronization time:

* You're not only downloading data, but the data is also being validated. There is a lot of I/O going on. Disk speed is a significant factor.
* The earlier blocks are much smaller than the later blocks. Validation time roughly scales linearly with the data size.
* Complexity of transactions may have increased over time, transactions with more inputs take significantly more time to validate.
* The UTXO database grows larger as you parse the blockchain, and every input for every transaction has to be looked up in the UTXO database.


---

