The word “blockchain” is everywhere these days, but when it comes to explaining exactly what it is, many people get stuck. This article explains in plain language how blockchains keep records, why they’re difficult to alter, and what they can—and can’t—prove.

Bitcoin was the first blockchain system to operate at scale, $BTC is the native coin of the Bitcoin network. Current price: 77,432.01 (24h +0.57%).

▍A ledger maintained collectively

You can think of a blockchain as a public ledger. Unlike a bank, which keeps its records on its own servers, this ledger is maintained collectively by many nodes. Every full node stores a complete copy of the records, which anyone can download and verify.

Bitcoin was the first blockchain to operate at scale. Satoshi Nakamoto published the Bitcoin white paper on October 31, 2008. On January 3, 2009, the first block (the genesis block) was mined, and it included a headline from that day's issue of The Times.

▍Where “block” and “chain” come from

Transactions aren’t added to the ledger one by one. Instead, they’re first bundled into blocks. Bitcoin produces a block about every 10 minutes on average. After Ethereum switched to proof of stake in 2022, it began scheduling blocks in 12-second slots.

Each block records the hash of the previous block. A hash can be thought of as a “fingerprint” of a piece of data: change even a single character, and the fingerprint will be completely different. Blocks are linked together, one after another, to form a chain.

▍Why it’s hard to tamper with

If someone tries to alter a block in the past, its hash changes, and the “previous hash” recorded in every block after it no longer matches. To reconnect the ledger, they would have to redo all the subsequent blocks.

In proof-of-work networks like Bitcoin, redoing blocks requires real computing power, and the attacker must also catch up with the main chain as it continues to grow across the network. The deeper a block is buried, the more costly it is to rewrite—which is why recipients typically wait for several confirmations.

▍What it can and can’t prove

Anyone can look up transactions on a public blockchain, but an address isn’t directly linked to a real-world identity. That’s why blockchains are often described as “transparent and public, but not tied to real names.”

One more point is easy to misunderstand: being recorded on a blockchain only means that the record will be difficult to change afterward. It doesn’t mean the information itself is true. Projects that tout “blockchain” still require you to check where the money is going.

▍Summary

Understanding how a blockchain keeps its ledger won’t make you money overnight, but it can help you distinguish technical facts from claims that merely borrow the concept. Don’t put all your money on a single judgment.

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