Ledger

A ledger is a record of financial transactions, and in the context of cryptocurrency it refers to the underlying database that a blockchain maintains to track every transfer of value that has ever occurred on the network. Unlike a traditional ledger kept by a single bank or institution, a blockchain ledger is distributed, meaning thousands of computers around the world hold identical copies of it, and it is updated through consensus rather than by a central authority.

The defining property of a blockchain ledger is that it is append-only. New transactions can be added to the end of the chain, but existing entries cannot be altered or deleted once they are confirmed and buried under enough subsequent blocks. This immutability is enforced through cryptographic hashing, where each block contains a reference to the hash of the previous block, so that changing any past transaction would require recalculating every block that came after it across a majority of the network, an effort that becomes computationally impossible as the chain grows.

This is often described as a distributed ledger, and it is the core innovation that allows cryptocurrencies to function without a central bank or clearing house verifying every transaction. Instead, network participants, whether miners in a proof-of-work system or validators in a proof-of-stake system, independently verify and record transactions according to the same shared rules, and the resulting ledger becomes the single source of truth that all participants can trust without needing to trust each other directly.

Beyond cryptocurrency, the term ledger also appears in hardware wallet products, most famously devices made by the company Ledger, which store a user’s private keys offline in a secure chip. This is a separate but related use of the word, referring to a physical device rather than the transaction record itself.

Because every transaction on a public blockchain ledger is visible to anyone who wants to look, blockchains are often described as transparent, even though the identities behind wallet addresses usually remain pseudonymous. Anyone can use a block explorer to browse the ledger and verify balances, transaction histories, and the total supply of a given cryptocurrency at any point in time.

Understanding the ledger as the foundational record-keeping layer of a blockchain helps explain why cryptocurrencies are considered resistant to fraud, double-spending, and unilateral rewriting of history, and why trust in the system comes from mathematics and distributed verification rather than from a single trusted institution.