Picture a shared ledger written in bound pages. Each page holds a batch of entries, and every new page opens by referencing the previous one, so the pages can only be read in one order. A block is that page. It carries a list of transactions plus a compact header: a timestamp, a fingerprint of the transactions inside, and the fingerprint of the block that came before.
New blocks are proposed by whoever the network's <a href="/glossary/consensus/">consensus</a> rules select — miners under proof of work, validators under proof of stake — and the rest of the network checks the result before accepting it. The producer usually collects a <a href="/glossary/block-reward/">block reward</a> plus the fees attached to the transactions they chose to include. That payment is the incentive that keeps blocks coming.
Blocks arrive on a rough schedule rather than a strict one, and the target interval differs from chain to chain. Because each block commits to the one before it, editing an old transaction would mean redoing every block since — which is why people talk about a payment gaining security as more blocks pile on top.
One block is a first confirmation, not a guarantee; several blocks later, reversing it becomes impractical rather than merely unlikely. Anyone can inspect the contents of a specific block through a <a href="/glossary/block-explorer/">block explorer</a>, which is the quickest way to check whether a transaction actually landed or is still waiting.
Key takeaways
- A block's header contains the fingerprint of the previous block, which is the mechanical reason history cannot be quietly edited.
- Waiting for extra blocks after receiving a large payment is a practical security setting, not a superstition.
- If a transaction appears in no block at all, it was never confirmed — it may still be queued, or it may have been dropped.
Block — frequently asked questions
How long does one block take?
It depends entirely on the chain. Each network targets an average interval and adjusts its difficulty or scheduling to stay near it, but individual blocks arrive early or late because block production is probabilistic rather than clockwork. That is why a transfer can confirm almost immediately one time and take noticeably longer the next, even with a similar fee attached.
What happens to my transaction if a block is full?
It waits. Blocks have a size or gas limit, so when demand is high the transactions offering higher fees are packed in first and the rest stay queued. Yours is not lost — it simply has not been included yet. Most wallets let you resubmit with a higher fee, and some chains let you replace the pending transaction outright.
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