{"number":34,"title":"Block v2, Height in Coinbase","authors":["Gavin Andresen"],"status":"Deployed","type":"Specification","layer":"Consensus (soft fork)","created":"2012-07-06","requires":[],"replaces":[],"replacedBy":[],"discussion":[],"abstract":"Bitcoin blocks and transactions are versioned binary structures. Both currently use version 1. This BIP introduces an upgrade path for versioned transactions and blocks. A unique value is added to newly produced coinbase transactions, and blocks are updated to version 2.","eli5":"Upgraded blocks to version 2 and required each block's coinbase transaction (the one paying the miner) to include the block's height. This makes every coinbase unique, preventing duplicate transactions, and set a pattern for rolling out later upgrades.","categories":["consensus","blocks","validation"],"filename":"bip-0034.mediawiki","githubUrl":"https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki","format":"mediawiki","readingMinutes":1,"inbound":4,"revisions":16,"impact":85,"core":false,"references":[],"lastModified":"2025-10-08","html":"

Abstract

\n

Bitcoin blocks and transactions are versioned binary structures. Both currently use version 1. This BIP introduces an upgrade path for versioned transactions and blocks. A unique value is added to newly produced coinbase transactions, and blocks are updated to version 2.

\n

Motivation

\n
  1. \nClarify and exercise the mechanism whereby the bitcoin network collectively consents to upgrade transaction or block binary structures, rules and behaviors.\n
\n
  1. \nEnforce block and transaction uniqueness, and assist unconnected block validation.\n
\n

Specification

\n
  1. \nTreat transactions with a version greater than 1 as non-standard (official Satoshi client will not mine or relay them).\n
\n
  1. \nAdd height as the first item in the coinbase transaction's scriptSig, and increase block version to 2. The format of the height is \"minimally encoded serialized CScript\" -- first byte is number of bytes in the number (will be 0x03 on main net for the next 150 or so years with 223-1 blocks), following bytes are little-endian representation of the number (including a sign bit). Height is the height of the mined block in the block chain, where the genesis block is height zero (0).\n
\n
  1. \n75% rule: If 750 of the last 1,000 blocks are version 2 or greater, reject invalid version 2 blocks. (testnet3: 51 of last 100)\n
\n
  1. \n95% rule (\"Point of no return\"): If 950 of the last 1,000 blocks are version 2 or greater, reject all version 1 blocks. (testnet3: 75 of last 100)\n
\n

Backward compatibility

\n

All older clients are compatible with this change. Users and merchants should not be impacted. Miners are strongly recommended to upgrade to version 2 blocks. Once 95% of the miners have upgraded to version 2, the remainder will be orphaned if they fail to upgrade.

\n

Implementation

\n

https://github.com/bitcoin/bitcoin/pull/1526

\n

Result

\n

Block number 227,835 (timestamp 2013-03-24 15:49:13 GMT) was the last version 1 block.

","toc":[{"id":"abstract","title":"Abstract","level":2},{"id":"motivation","title":"Motivation","level":2},{"id":"specification","title":"Specification","level":2},{"id":"backward-compatibility","title":"Backward compatibility","level":2},{"id":"implementation","title":"Implementation","level":2},{"id":"result","title":"Result","level":2}],"history":{"totalCommits":16,"firstCommit":"2012-07-06T20:06:10+02:00","lastUpdated":"2025-10-08T14:59:36-07:00","events":[{"sha":"24e96e870fffaa257b465ce1f0370c14aac588e8","date":"2025-10-08T14:59:36-07:00","author":"Murch","message":"process: Created ↦ Assigned","url":"https://github.com/bitcoin/bips/commit/24e96e870fffaa257b465ce1f0370c14aac588e8","kind":"edit"},{"sha":"5207ef92a52d0b8902895b0dbb40823a4d698ec9","date":"2025-04-11T20:08:17-07:00","author":"Murch","message":"process: Author ↦ Authors","url":"https://github.com/bitcoin/bips/commit/5207ef92a52d0b8902895b0dbb40823a4d698ec9","kind":"edit"},{"sha":"59730dec4fb641a41589aa1b91d3c452f13e0e36","date":"2025-04-11T20:05:13-07:00","author":"Murch","message":"process: Remove Comments-URI and -Summary","url":"https://github.com/bitcoin/bips/commit/59730dec4fb641a41589aa1b91d3c452f13e0e36","kind":"edit"},{"sha":"a233bde4af52c6a11269e2e6dd9707abce441ffe","date":"2025-04-11T18:19:21-07:00","author":"Murch","message":"process: Standards Track ↦ Specification","url":"https://github.com/bitcoin/bips/commit/a233bde4af52c6a11269e2e6dd9707abce441ffe","kind":"edit"},{"sha":"5d3ceb37734f80b2ec206fc94245e3bfd6d5b0f0","date":"2025-04-11T18:08:44-07:00","author":"Murch","message":"process: Final/Active ↦ Deployed","url":"https://github.com/bitcoin/bips/commit/5d3ceb37734f80b2ec206fc94245e3bfd6d5b0f0","kind":"status"},{"sha":"08844fd6eff55e756c453c6d2e16de40e8f80e73","date":"2020-11-18T12:17:04-08:00","author":"Greg-Griffith","message":"BIP34 specifies it requires minimal encoding.","url":"https://github.com/bitcoin/bips/commit/08844fd6eff55e756c453c6d2e16de40e8f80e73","kind":"edit"},{"sha":"959fecc15bdad070afa63455468b1dba54655fa6","date":"2016-11-30T09:47:31+00:00","author":"Luke Dashjr","message":"Promote BIP 2 Draft->Active, and implement it","url":"https://github.com/bitcoin/bips/commit/959fecc15bdad070afa63455468b1dba54655fa6","kind":"status"},{"sha":"72f18918a8ae655212ea2700b30f0dc4d758b843","date":"2016-11-30T09:45:33+00:00","author":"Luke Dashjr","message":"Promote BIP 123 Draft->Active, and implement it","url":"https://github.com/bitcoin/bips/commit/72f18918a8ae655212ea2700b30f0dc4d758b843","kind":"status"},{"sha":"2d909ad98a999a77bfcf8393a60166f1eabd22a4","date":"2016-02-05T02:13:31+08:00","author":"Johnson Lau","message":"BIP34 correction","url":"https://github.com/bitcoin/bips/commit/2d909ad98a999a77bfcf8393a60166f1eabd22a4","kind":"edit"},{"sha":"f31f7d43473fadcfafbc886b15e8c488654839c2","date":"2016-02-01T20:14:22+00:00","author":"Luke Dashjr","message":"Promote Accepted->Final BIPs 11, 14, 21, 22, 23, 31, 32, 34, 35, 37, 65","url":"https://github.com/bitcoin/bips/commit/f31f7d43473fadcfafbc886b15e8c488654839c2","kind":"status"},{"sha":"e6cf789167ab9d22f6807cea02c48017613aab94","date":"2014-11-11T10:15:58-05:00","author":"Gavin Andresen","message":"Added Result section, noting last v=1 block","url":"https://github.com/bitcoin/bips/commit/e6cf789167ab9d22f6807cea02c48017613aab94","kind":"edit"},{"sha":"d9e890a8f27e46806238e298a346397871fd7e87","date":"2013-10-21T02:18:47-04:00","author":"Peter Todd","message":"Fix formatting","url":"https://github.com/bitcoin/bips/commit/d9e890a8f27e46806238e298a346397871fd7e87","kind":"edit"},{"sha":"981d619665a1cbbad1c0758c8ebb73cdc3c6b828","date":"2013-10-21T00:53:42-04:00","author":"Peter Todd","message":"Archive Revision as of 14:58, 18 January 2013","url":"https://github.com/bitcoin/bips/commit/981d619665a1cbbad1c0758c8ebb73cdc3c6b828","kind":"edit"},{"sha":"1f64d2b06d628dffdc297be9a8afbb9da4e6b6ca","date":"2013-10-21T00:32:10-04:00","author":"Peter Todd","message":"Rename to mediawiki extension","url":"https://github.com/bitcoin/bips/commit/1f64d2b06d628dffdc297be9a8afbb9da4e6b6ca","kind":"rename"},{"sha":"e81db32a42e95de3abe33a055c61548f2d59a536","date":"2012-08-27T22:54:22+01:00","author":"Amir Taaki","message":"BIP 34 -> Accepted","url":"https://github.com/bitcoin/bips/commit/e81db32a42e95de3abe33a055c61548f2d59a536","kind":"edit"},{"sha":"61aeaf653b18f35189d9f7178ab1710b25a6257f","date":"2012-07-06T20:06:10+02:00","author":"Amir Taaki","message":"BIP 34 - heights in block coinbase tx inputs.","url":"https://github.com/bitcoin/bips/commit/61aeaf653b18f35189d9f7178ab1710b25a6257f","kind":"edit"}]}}