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One question
How does Bitcoin prevent an output being spent twice?
Understand UTXOs, independent validation and accumulated work.
- Unspent outputsConsumes→
- TransactionCreates→
- New outputs
Bitcoin transactions consume unspent outputs and create new ones. Each output can be spent only once in the valid chain. Full nodes validate the rules independently; accumulated work helps select among valid branches.
As a teaching analogy, exchanging old tickets for new ones differs from editing an account balance. The analogy illustrates linked outputs, not a claim that an output represents a physical ticket.
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Must a full node accept every block a miner broadcasts?
No. It independently validates blocks and transactions.
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