{"number":102,"title":"Block size increase to 2MB","authors":["Jeff Garzik"],"status":"Closed","type":"Specification","layer":"Consensus (hard fork)","created":"2015-06-23","requires":[],"replaces":[],"replacedBy":[],"discussion":[],"abstract":"Simple, one-time increase in total amount of transaction data permitted in a block from 1MB to 2MB.","eli5":"Proposed a single, simple increase in the maximum block size from 1 MB to 2 MB to allow more transactions per block. Being a change that older software would reject, it would have required a hard fork, and it was one of the competing options in the block size debate.","categories":["capacity","blocks"],"filename":"bip-0102.mediawiki","githubUrl":"https://github.com/bitcoin/bips/blob/master/bip-0102.mediawiki","format":"mediawiki","readingMinutes":1,"inbound":1,"revisions":13,"impact":46,"core":false,"references":[],"lastModified":"2025-10-08","html":"

Abstract

\n

Simple, one-time increase in total amount of transaction data permitted in a block from 1MB to 2MB.

\n

Motivation

\n
  1. \nContinue current economic policy.\n
\n
  1. \nExercise hard fork network upgrade.\n
\n

Specification

\n
  1. \nMAX_BLOCK_SIZE increased to 2,000,000 bytes at trigger point.\n
\n
  1. \nIncrease maximum block sigops by similar factor, preserving SIZE/50 formula.\n
\n
  1. \nTrigger: (1) Block time 00:00:00 on flag day, AND (2) 95% of the last 1,000 blocks have signaled support.\n
\n

Backward compatibility

\n

Fully validating older clients are not compatible with this change. The first block exceeding 1,000,000 bytes will partition older clients off the new network.

\n

Discussion

\n

In the short term, an increase is needed to continue to current economic policies with regards to fees and block space, matching market expectations and preventing market disruption.

\n

In the long term, this limit should focus on reflecting the maximum network engineering limit.

\n

Implementation

\n

https://github.com/jgarzik/bitcoin/tree/2015_2mb_blocksize

","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":"discussion","title":"Discussion","level":2},{"id":"implementation","title":"Implementation","level":2}],"history":{"totalCommits":13,"firstCommit":"2015-06-23T18:18:39-04:00","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":"66defbdc03ad64ccddfd373e1c59af9a41ab990f","date":"2025-04-11T18:11:55-07:00","author":"Murch","message":"process: Deferred/Obsolete/Rejected/Replaced/Withdrawn ↦ Closed","url":"https://github.com/bitcoin/bips/commit/66defbdc03ad64ccddfd373e1c59af9a41ab990f","kind":"status"},{"sha":"2eca4d32c8284952ba4cbe19a1db7a23767482b9","date":"2019-09-19T22:16:51+00:00","author":"Luke Dashjr","message":"Update BIP 102 status Draft->Rejected","url":"https://github.com/bitcoin/bips/commit/2eca4d32c8284952ba4cbe19a1db7a23767482b9","kind":"status"},{"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":"5cdae758f3941272962beb28897b2ae03189712e","date":"2015-12-18T08:39:00-05:00","author":"Jeff Garzik","message":"BIP 102: 95% update req","url":"https://github.com/bitcoin/bips/commit/5cdae758f3941272962beb28897b2ae03189712e","kind":"edit"},{"sha":"32112987af3ba178661e3f1f1f2616ecab547f8f","date":"2015-12-18T08:01:30-05:00","author":"Jeff Garzik","message":"BIP 102: remove dynamic adjustment","url":"https://github.com/bitcoin/bips/commit/32112987af3ba178661e3f1f1f2616ecab547f8f","kind":"edit"},{"sha":"097983d2563ea0a11ad3bc0add9946c8232e3e17","date":"2015-12-17T23:21:13-05:00","author":"Jeff Garzik","message":"BIP 102: update to match implementation","url":"https://github.com/bitcoin/bips/commit/097983d2563ea0a11ad3bc0add9946c8232e3e17","kind":"edit"},{"sha":"aad81251a18c47462055eb63eb2280570662f053","date":"2015-11-06T23:03:52-05:00","author":"Jeff Garzik","message":"BIP 102: Add miner vote. Fix index.","url":"https://github.com/bitcoin/bips/commit/aad81251a18c47462055eb63eb2280570662f053","kind":"edit"},{"sha":"188ee9e718dc12c34d86c2f4886c79c476437f0a","date":"2015-06-23T18:18:39-04:00","author":"Jeff Garzik","message":"bip-XX-2mb assigned BIP number 102.","url":"https://github.com/bitcoin/bips/commit/188ee9e718dc12c34d86c2f4886c79c476437f0a","kind":"edit"}]}}