Bitcoin btc

Bitcoin is a form of digital money that lets people send value directly to one another over the internet. It does not require a bank, card network, or other central intermediary to authorize every payment. The word Bitcoin can refer to the open network and protocol, while bitcoin (BTC) is the unit recorded and transferred on that network.

Instead of keeping balances in one company's database, Bitcoin uses a shared public ledger called the blockchain. Computers around the world independently keep and verify copies of this ledger, applying the same rules to transactions. Digital signatures prove that a payment was authorized by the holder of the relevant private key.

Bitcoin was introduced by the pseudonymous creator Satoshi Nakamoto. Its software is open source, so anyone can inspect, run, or modify a copy, although changes to the network's common rules require broad voluntary agreement from users, node operators, and miners. No single person or company owns or controls the network.

Bitcoin is designed to combine peer-to-peer payments with predictable scarcity. Units can be divided into 100 million satoshis, allowing very small amounts to be sent. Bitcoin can be used for payments, settlement, or as an asset people choose to hold, but its market price is volatile and its future adoption is not guaranteed.

Bitcoin addresses several limitations of traditional digital payments. First, ordinary digital files can be copied, so a digital money system needs a reliable way to prevent the same unit from being spent twice. Bitcoin solves this digital-scarcity problem with a shared transaction history, cryptographic signatures, and proof-of-work-based consensus. Second, it enables peer-to-peer money: users can transmit value globally without needing a bank or payment processor to approve or reverse each transfer. Third, its monetary issuance and transaction rules are public and predictable rather than being controlled by a central authority that can change the supply or block individual payments at will. Users still rely on software, exchanges, custodians, and local laws in many situations, and Bitcoin does not eliminate every payment risk.

A wallet manages private keys and creates transactions; it does not literally hold coins in a physical place. A transaction spends previously created unspent outputs and assigns them to new outputs protected by the recipient's address or script. The transaction is signed with the sender's private key, broadcast to the peer-to-peer network, and checked by nodes against Bitcoin's rules.

Miners collect valid pending transactions into a candidate block and use specialized hardware to search for a proof-of-work hash below the network's target. Finding a valid block is intentionally difficult, but checking the result is easy. The winning block includes the hash of the prior block, linking the history together. Nodes accept valid blocks and generally follow the chain with the most accumulated proof of work, making older records increasingly costly to rewrite. Difficulty adjusts every 2,016 blocks so the long-run target remains about one block every 10 minutes.

New bitcoin enters circulation through the block subsidy paid in a valid block, together with transaction fees. The subsidy is cut in half every 210,000 blocks, approximately every four years. This scheduled halving makes issuance decline over time; under the protocol's subsidy schedule, total issuance approaches and is capped at 21 million BTC. The 21-million limit is a protocol rule enforced by validating nodes, not a promise made by a central issuer.