Note: This is the old version of the website. It will be taken offline on 01 May 2024. If there is anything on this website that you use and cannot find on the new version, please let me know at gregabc@learnme­

  • Hash256
  • Hash160
  • Reverse Bytes
  • Hexadecimal
  • Satoshis

The Blockchain

A shared file of bitcoin transactions.

What is the blockchain?

The blockchain is a file that contains a list of every bitcoin transaction ever made.

The blockchain

Everyone on the bitcoin network shares a copy of this file, and it updates regularly with the latest transactions.

The Bitcoin Network: Everyone sharing a file of transactions (called the blockchain).

Why is the blockchain important?

The blockchain tells you how many bitcoins each person owns.

This is because having a complete list of transactions allows you to work out how many bitcoins are located at each address. Therefore, you can figure out how many bitcoins each person has.

The blockchain is like a logbook, or a ledger.

Ledger – a book in which the monetary transactions of a business are posted in the form of debits and credits.

Why is it called the blockchain?

Because transactions aren’t added to the file individually. Instead, they are bunched together and added in blocks. Hence, blockchain.

Also, these blocks are linked together, so any changes made to a block lower down the chain will change the blocks above it. So linkedblocks, or blockchain.

Transactions are added to in blocks, and these blocks are chained together.

The block-ing of transactions makes it easier for everyone to share a copy of the blockchain. With the Internet connection speeds we’ve got, it’s much easier to share a file that updates once every 10 minutes, than one that updates multiple times a second.

The chaining of transactions is a security feature. It makes it difficult to tamper with the blockchain without anyone noticing.

How is the blockchain shared?

The blockchain is shared by the nodes on the bitcoin network, in the same way a totally legit and non-copyrighted video file might be shared on the BitTorrent network.

Bitcoin peer-to-peer file sharing of the blockchain. If my file hasn’t got the latest blocks of transactions, someone will share them with me.

P2P file sharing is a topic of it’s own, but for now just know that the blockchain is shared like a BitTorrent file across the bitcoin network.

Where can I get a copy of the blockchain?

You can get your own copy of a genuine, bona fide, electrified monorail blockchain by downloading the original bitcoin client.

Once installed and running, the client will connect to the network and start downloading the blockchain. It’s 180+GB, so give it some time.

When the download finishes you’ll have a complete copy of the blockchain, and a list of every bitcoin transaction ever made is in your hands. Furthermore, every time you run the bitcoin client you will be helping to share this file with everyone else joining the network. Some of your friends may even start calling you a “Full Node”.

By keeping a copy of the blockchain and sharing it with other people on the network, you make bitcoin stronger.

If you’re a fan of bittorrent, you could think of yourself as seeding the blockchain. Everyone loves a seeder.

Where is the blockchain file stored on my computer?

The blockchain is stored in files with names like this: blk00000.dat. There’s also blk00001.dat, blk00002.dat, and so on. (It’s split in to multiple files because it’s easier than working with one huge file.)

Their location depends on what operating system you’re using:

~/Library/Application Support/Bitcoin/

However, these .dat files contain data that is designed for a computer to read, so if you open one you’ll see a lot of mumbo-jumbo. But trust me, all the transactions are in there.

If you want to browse around a readable version of the blockchain, try my blockchain explorer. I basically take the data from the blk*.dat files (the very same copies you have), parse them, and display the contents on a web page.

By Greg Walker,

Last Updated: 21 Jul 2020
  • 21 Jul 2020: redirected and renamed files from /guide/ to /technical/
  • 28 Mar 2020: updated html for h1 headers and subheadings - now dynamic from yaml
  • 28 Mar 2020: updated html for h1 headers and subheadings
  • 09 Oct 2019: renamed browser to explorer, glossary to guide, and guide to beginners
Back to Top

Hey there, it's Greg.

I'll let you know about cool website updates, or if something seriously interesting happens in bitcoin.

Don't worry, it doesn't happen very often.