Bitcoin Core

Bitcoin Core is an open-source full node with a built-in wallet. It downloads and verifies every block since 2009, enforces the consensus rules, relays transactions and exposes an interface for wallets, exchanges and miners. It grew out of the client Satoshi Nakamoto released in 2009 and took the name Bitcoin Core in 2014. Most of the network's nodes run it or a close derivative.

Development happens in public on GitHub. Anyone can propose changes, which are reviewed by other contributors and merged by a small group of maintainers; funding comes from grants and companies rather than a foundation that controls the protocol. New major versions are released roughly twice a year, and consensus changes are proposed separately through BIPs and require broad agreement to activate.

Its dominance is debated. Supporters say a single careful implementation avoids dangerous consensus splits; critics worry about concentrated influence over defaults. In 2025, Bitcoin Core's decision to relax its default OP_RETURN data limit pushed some node operators to alternatives such as Bitcoin Knots. Running Core does not mean agreeing with every policy, since many settings can be changed.