The blockchain is Bitcoin's shared history: blocks of transactions, each linked to the one before by its hash. Learn how it works and why it is hard to change.
A chain of blocks
Every 10 minutes or so, a new block of transactions is added to Bitcoin's history. Each block contains the hash of the block before it, so the blocks form a chain going all the way back to the The genesis block.
Why the links matter
A hash is a fingerprint of data. If someone changed an old transaction, that block's hash would change, which would break the link from the next block, and the next, all the way to today. To hide the change, they would have to redo the Proof of work for every block since. That's what makes the history so hard to rewrite.
Who has a copy?
Every full node. There is no master copy. When nodes disagree, for example when two blocks are found at once, they follow the valid chain with the most work.
How big is it?
The full Bitcoin blockchain is several hundred gigabytes and grows every day. You can also run a pruned node that verifies everything but deletes old blocks.
Our own copy
MyBitcoinExplorer runs its own Bitcoin Core node. You can watch its progress on our status page and browse the latest blocks it has verified.
Blockchain vs a normal database
| Bitcoin blockchain | Company database | |
|---|---|---|
| Who can write | Any miner who does the work | The company |
| Who can read | Everyone | Usually only the company |
| Editing old records | Practically impossible | Easy for the owner |
| Copies | Thousands, kept independently | A few, kept by one owner |
Is "blockchain" the same as Bitcoin?
No. Bitcoin uses a blockchain, but a blockchain alone doesn't make money trustworthy. Bitcoin's security comes from the combination of proof of work, independent nodes and fixed rules. Many "blockchains" have one company in control, which brings back the trust problem Bitcoin was built to remove.
Key takeaways
- The blockchain is a chain of blocks, each containing the previous block's hash.
- Changing old data would break every later link.
- Every full node keeps and verifies its own copy.
Common questions
Is the blockchain stored in one place?
No. Every full node stores its own copy and checks it independently.
Can the blockchain be edited?
Not without redoing the proof of work for every later block and overtaking the honest network, which is impractical.
How big is the Bitcoin blockchain?
The full blockchain requires hundreds of gigabytes and keeps growing as new blocks arrive. Check current storage requirements before choosing hardware.
Can I download the blockchain?
Yes. Installing Bitcoin Core and letting it sync downloads and verifies the whole history.