TERM_DEF // UPGRADES_BIPS / BIP_34_COINBASE_HEIGHT_BLOCK_V2
BIP 34 (COINBASE
HEIGHT, BLOCK V2)
HEIGHT, BLOCK V2)
block-v2/">BIP 34 (Coinbase Height, Block v2). Required block height in the coinbase scriptSig; first fork/">soft fork via version bits.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
WHAT_BIP_34_COINBASE_HEIGHT_BLOCK_V2_IS
BIP 34 (Coinbase Height, Block v2) — at a glance
UPGRADES
BIP 34 — "Coinbase Height, Block v2" is a proposal in the Consensus family, first published in 2013 with status final (soft fork). Required block height in the coinbase scriptSig; first soft fork via version bits. Its technical mechanism: coinbase scriptSig MUST begin with the serialised block height; block version bumped to 2. silently enforced from height ~227,930 onward
Why it exists
DESIGN
BIP 34 (Coinbase Height, Block v2) exists to solve a specific problem: embed block height in the coinbase to prevent BIP-30 style duplicate-txid attacks. Without a written, numbered spec, every wallet and node implementer would interpret the requirement differently — and Bitcoin's value depends on every implementation agreeing exactly. BIP-34 is the single source of truth for this concern, so any new client built today can match the behaviour of every client built since 2013.
HOW_IT_WORKS
Mechanism
HOW IT WORKS
Mechanically, BIP-34 coinbase scriptSig MUST begin with the serialised block height; block version bumped to 2. Because this is a soft fork, old software accepts new behaviour without modification — but new behaviour is rejected if old software produces it. Adoption today: silently enforced from height ~227,930 onward.
1. Author drafts BIP-34 against the BIP-2 template — abstract, motivation, specification, rationale.
2. The text + a reference implementation are posted on the bitcoin-dev list and as a PR to bitcoin/bips.
3. Reviewers tear it apart: ambiguities, security concerns, edge cases, interaction with prior BIPs.
4. Once stable, the BIP editor merges it; it gets a number (BIP-34) and the status "draft" or "proposed".
5. Implementations land in Bitcoin Core / wallets / other clients. For consensus changes: activation parameters chosen.
6. After deployment + adoption, BIP-34 is promoted to "final"; deprecated proposals get "replaced" or "withdrawn".
WORKED_EXAMPLE
BIP-34 — quick reference card
EXAMPLE
BIP number : 34
Title : Coinbase Height, Block v2
Area : Consensus
First published: 2013
Status : final
Fork class : soft
Motivation : embed block height in the coinbase to prevent BIP-30 style duplicate-txid attacks.
Mechanism : coinbase scriptSig MUST begin with the serialised block height; block version bumped to 2.
Where it shows up : silently enforced from height ~227,930 onward.
Read the spec : https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki
KEY_PROPERTIES
OPT-IN
No authority can force a BIP on anyone. Adoption depends entirely on whether the change is genuinely useful.
NUMBERED
Stable numeric reference — BIP-34 means the same thing across every wallet, miner, and node that has read this spec.
CONSENSUS
BIP-34 is a soft fork — it changes (or proposes to change) the rules every full node enforces.
DEPLOYED
Implementations of BIP-34 are in production. The behaviour is observable on mainnet today.
COMMON_PITFALLS
Things that catch people out
PITFALLS
- BIP-34 is a soft fork — old clients accept new behaviour but don't enforce it. Validate against an upgraded node to be sure the rule is being checked.
- Don't confuse "draft" / "proposed" / "final" status — read the BIP header before relying on it in production.
- The BIP number is just an editorial counter — it doesn't imply correctness or stability. Always cross-reference with the latest bitcoin/bips repo.
RELATED_CONCEPTS
Other terms from Upgrades & BIPs — click any to read its page:
TERMINOLOGY_INDEX
TERMINOLOGY
BIP 34 (Coinbase Height, Block v2)
Required block height in the coinbase scriptSig; first soft fork via version bits.
Segregated Witness (SegWit, BIP 141)
The 2017 upgrade separating witness-data/">witness data, fixing tx malleability, and introducing weight units.
Taproot (BIP 341)
Tapscript (BIP 342)
Script-language updates accompanying Taproot — new opcodes, removed limits.
Schnorr (BIP 340)
The Schnorr signature spec adopted by Taproot.
BIP Process
The community workflow for proposing, discussing, and tracking changes to Bitcoin.
Soft Fork Activation
MASF (Miner-Activated Soft Fork)
Activation triggered by miner signaling in block versions.