> For the complete documentation index, see [llms.txt](https://protocol.bsvblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://protocol.bsvblockchain.org/introduction.md).

# Introduction

This is a technical reference for the protocol of the BSV blockchain, an implementation of the original Bitcoin protocol.

The **protocol** is the set of rules that determine whether a **transaction** or a **block** is valid. A transaction that is valid under these rules remains valid permanently. Anything that does not affect the validity of a transaction or block — network transport, RPC interfaces, wallets, and miner-configurable policy — is outside the scope of this reference and is noted as such where it appears.

The reference is organised into three parts, plus a separate networking section:

* [**Specification**](/specification/transactions.md) — the byte-exact, code-cited protocol: transaction and block structure, Script, opcodes, signature hashing, the consensus rules that determine validity, and the upgrade history that says which rules apply at which block height. This is the validity contract.
* [**Concepts**](/concepts/concepts.md) — conceptual background: the UTXO model, proof of work, the economic model, common transaction templates, privacy, and digital asset recovery. Context for reading the specification, not the contract itself.
* [**Implementation Notes**](/implementation-notes/policy-vs-consensus.md) — non-consensus material: the consensus-versus-policy distinction, how the reference node operates, and light-client/SPV verification.

Separately, [**Peer-to-Peer Networking**](/peer-to-peer-networking/p2p.md) documents how nodes transport data between each other — the SV Node wire protocol, and later the Teranode networking layer. This is **not** part of the protocol: the network transport has no bearing on whether a transaction or block is valid. It is included here to keep the networking documentation alongside the rest of the reference.

Every concrete value in the Specification is cited to the reference node implementation, [`bitcoin-sv/bitcoin-sv`](https://github.com/bitcoin-sv/bitcoin-sv), pinned to a specific release commit.

The reference implementation and specifications are maintained by the BSV Association. Further information: [bsvblockchain.org](https://www.bsvblockchain.org).