Satoshi's paper says:

Once the latest transaction in a coin is buried under enough blocks, the spent transactions before it can be discarded to save disk space.

What are spent transactions?

1 Answer 1


Balances in Bitcoin are stored in Unspent Transaction Outputs . UTXO can be used as inputs when a transaction is created. They can only be spent completely, while the resulting transaction creates new ones in the process, redistributing the balance to the recipients of the transaction. Spent transactions refers to Transaction Outputs that have been expended.

  • @green Note that this way of saving disk space as Satoshi described it is not actually used as such. Bitcoin simply keeps a separate UTXO database and basically only keeps the original blocks (with the actual transactions) to be able to upload them to any per asking for them. Recent Bitcoin Core versions do have the ability to simply completely delete really old blocks. This is called purging.
    – Jannes
    Commented Sep 8, 2015 at 3:23

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