user114595: Somebody asked me about Bitcoin and I explained to him many many computers are connected to the Blockchain to keep records of all the accounts (or to keep addresses of the bitcoin and owner?). But how many computers are connected to it, as of recently or 2020?

user63872: Computers are not 'connected to the blockchain', as that implies that the blockchain is some sort of central entity in the network.
In reality, the network is just made up of a huge number of peers, known as 'nodes'. A 'full node' is one which has fully verified the state of the network, by working to verify all transactions that have occurred since the genesis block.
So each node keeps its own copy of the blockchain, and is connected to other nodes, which each have their own copy as well. The rules of the network work to allow these nodes to all remain in consensus about what that blockchain looks like, despite the fact they each keep their own record of it.
How many nodes are there? It's tough to say. Many nodes are made to be intentionally hidden, for security or privacy reasons. Many exist on the tor network, and some receive their information via satellite feed. Some websites will query nodes on the network in an attempt to figure out numbers, but ultimately the answer to this question is not really knowable for certain.
See for example:

https://luke.dashjr.org/programs/bitcoin/files/charts/historical.html
https://coin.dance/nodes
https://bitnodes.io/


user208: 
Somebody asked me about Bitcoin and I explained to him many many computers are connected to the Blockchain to keep records of all the accounts (or to keep addresses of the bitcoin and owner?).

The blockchain is the data structure they collectively maintain. It is not an "entity" that can be connected to. The nodes are just connected to each other, and tell each other about updates they learn about.
It's hard to count how many nodes there actually are. There are sites like https://bitnodes.io that keep track of reachable nodes. However, there are many nodes on the network that only connect out to others but can't be connected to; probably in the 100000s.
A further complication is that not all of these nodes are equally relevant. It's easy to spin up a few hundred nodes on AWS, that nobody uses for anything, but do make it look like there are lots of independent users. Worse, there are also a lot of spy nodes on the network that don't do any work, except trying to monitor which nodes are the origin of particular transactions.
In the end, if you run a node yourself, it doesn't matter. It validates everything the network tells it, so if you do that, the part that matters is: 1 node, your own.

114595: <p>Somebody asked me about Bitcoin and I explained to him many many computers are connected to the Blockchain to keep records of all the accounts (or to keep addresses of the bitcoin and owner?). But how many computers are connected to it, as of recently or 2020?</p>
 63872: <p>Computers are not 'connected to the blockchain', as that implies that the blockchain is some sort of central entity in the network.</p>
<p>In reality, the network is just made up of a huge number of peers, known as 'nodes'. A 'full node' is one which has fully verified the state of the network, by working to verify all transactions that have occurred since the genesis block.</p>
<p>So each node keeps its own copy of the blockchain, and is connected to other nodes, which each have their own copy as well. The rules of the network work to allow these nodes to all remain in consensus about what that blockchain looks like, despite the fact they each keep their own record of it.</p>
<p>How many nodes are there? It's tough to say. Many nodes are made to be intentionally hidden, for security or privacy reasons. Many exist on the tor network, and some receive their information via satellite feed. Some websites will query nodes on the network in an attempt to figure out numbers, but ultimately the answer to this question is not really knowable for certain.</p>
<p>See for example:</p>
<ul>
<li><a href="https://luke.dashjr.org/programs/bitcoin/files/charts/historical.html" rel="nofollow noreferrer">https://luke.dashjr.org/programs/bitcoin/files/charts/historical.html</a></li>
<li><a href="https://coin.dance/nodes" rel="nofollow noreferrer">https://coin.dance/nodes</a></li>
<li><a href="https://bitnodes.io/" rel="nofollow noreferrer">https://bitnodes.io/</a></li>
</ul>
 208: <blockquote>
<p>Somebody asked me about Bitcoin and I explained to him many many computers are connected to the Blockchain to keep records of all the accounts (or to keep addresses of the bitcoin and owner?).</p>
</blockquote>
<p>The blockchain is the data structure they collectively maintain. It is not an &quot;entity&quot; that can be connected to. The nodes are just connected to each other, and tell each other about updates they learn about.</p>
<p>It's hard to count how many nodes there actually are. There are sites like https://bitnodes.io that keep track of <em>reachable</em> nodes. However, there are <em>many</em> nodes on the network that only connect out to others but can't be connected to; probably in the 100000s.</p>
<p>A further complication is that not all of these nodes are equally relevant. It's easy to spin up a few hundred nodes on AWS, that nobody uses for anything, but do make it look like there are lots of independent users. Worse, there are also a lot of spy nodes on the network that don't do any work, except trying to monitor which nodes are the origin of particular transactions.</p>
<p>In the end, if you run a node yourself, it doesn't matter. It validates everything the network tells it, so if you do that, the part that matters is: 1 node, your own.</p>
