Is blockchain.com the only place where you can see the blockchain?

Question

I've been investigating Bitcoin and when I would try to find out where the blockchain is stored, I was told that it is stored on everyone's computer. Then I would ask where was the blockchain stored on my computer and the response was it is stored in your wallet.

Since Bitcoin is decentralized, I supposed that it must be found anywhere. But I found no information about that.

My question is actually: Where can I see the blockchain without going to blockchain.com?

Answer 1

Blockchain.com is a wallet service and provides a "blockchain explorer". The company is named after the Bitcoin network's transaction journal, the blockchain.

Bitcoin is a permissionless peer-to-peer network. Users interact with the network by running software that implements the Bitcoin protocol.

There are various types of software that interact with the network to different degrees, but the backbone of the network are the so called "fully validating nodes" or fullnodes. Fullnodes distinguish themselves by downloading and verifying the complete blockchain. Archival nodes maintain a complete copy of the blockchain, while pruning nodes discard the oldest parts of the blockchain data after using it to calculate the current ledger. New nodes joining the network download the blockchain data from existing nodes.

Most Bitcoin software does not download, verify and store the complete blockchain. These "thin-clients" rely on other nodes or central services to serve data about the Bitcoin network's state to them. Wallet software (such as e.g. the Blockchain wallet) usually belongs to this category of node.

So, to answer your other question: your computer only stores the blockchain if you run a fullnode, e.g. Bitcoin Core. Then you can "see" the blockchain by requesting data from the fullnode. There are various projects that bundle visualization or blockexplorer software with the fullnode, to make the "seeing" part a bit more user friendly. ;)

Answer 2

Where can I see the blockchain without going to blockchain.com?

1. Other blockchain explorers

   Use your favourite search engine to find other "blockchain explorers"

2. If you run a full-node wallet like Bitcoin core

   Access your local copy of the blockchain. For example, Bitcoin core on Windows stores it in %APPDATA%\Bitcoin

   You can examine this copy using the bitcoin-core command line tools, The bitcoin-core debug console or a third party "blockchain parser"

Answer 3

The blockchain is information. It is not a "thing," and it is copied wherever one wishes to have it.

Distributed systems like this are interesting, and it may help to think about a heretical phrasing: a blockchain. That's right. There is more than one.

A blockchain is any set of information (i.e. bytes) which describes a valid block chain. There are two ways to identify them:

• There is the original block, a block chain of length 1, which was defined to be a valid block chain in Satoshi's original publication. This is called the genesis block for any block chain system (This could be seen as a minimal level of centralization, but we usually don't pay much attention to it)
• Any sequence of blocks which meets the mathematical requirements of a block chain and starts with Satoshi's original block is a valid block chain.

So how do we get from a blockchain to the blockchain? Bitcoin defines the longest block chain to be "the" block chain at any given moment. More precisely, it is the most difficult block chain. Each block includes the answer to a math problem that requires a great deal of computational work, and the sum of that work is used to identify which block chain is the "longest."

Now bitcoin has been around long enough and enough CPU time has been burned on one chain that we can be extraordinarily confident that it is indeed the longest block chain in the bitcoin universe. We call this "the blockchain."

Sites like the blockchain explorers listed in RedGrittyBrick's answer will show you a block chain that they assert is the blockchain. And, due to the raw length of the chain, and the solid agreement between the explorers, we can be quite confident it is "the" block chain.

At least, we can be confident up to the last few blocks. There are many rules of thumb for how deep a block has to be before it is deemed truly irrevocable. I've heard the number 6 blocks thrown around. The idea behind this is that its possible for people to disagree about the tail of the block chain, just due to networking issues. There may be several valid block chains floating around the world at any point in time which are vying for the title "The Blockchain."

The bitcoin algorithm is designed to resolve this. The honest miners will pick which chain to add to, and will select one chain (this chain is selected both by the desire of the miners to keep the algorithm working, and from raw greed -- mining on a chain which ends up not being "the chain" was wasteful)

Once enough blocks have been mined, it becomes increasingly unlikely that anyone will ever contest which chain is longer, and the longest re-earns the title "the block chain."

So really, the blockchain is wherever someone wants it. It's public knowledge, and can be downloaded from many sites, or from the peer to peer network itself. You can verify that it is indeed a valid block chain. And, as Murch points out in his answer, you can choose to run a "fullnode" which is a node in the peer to peer network which regularly maintains the block chain to the best of its ability.