Process & History

Bitcoin does not have a standards body that can decree a change. What it has is a written process, a classification of documents, and a few hard-won lessons about how rules actually activate on a live chain.

This chapter is the map of that process. BIP 3 is the current process document. BIP 123 explains how proposals are classified — consensus, peer services, API, applications — so you know what kind of thing you are reading. BIP 9 and BIP 8 describe version-bits activation, which is how most modern soft forks have been scheduled. BIP 90 is the cleanup that followed: once a deployment is buried under enough proof of work, nodes can stop carrying the old state machine.

BIP 50 sits next as a warning. It is the post-mortem of the March 2013 chain fork, when two versions of the software briefly disagreed about what a valid block was. The later activation BIPs make more sense after you have read that story.

The last two documents are the test networks wallets and nodes actually use. BIP 325 is Signet: a coordinated chain where blocks need a signature as well as proof of work. BIP 94 is Testnet 4, which replaced the old public testnet. Neither changes mainnet consensus.

In this chapter:

• BIP 3 — Updated BIP Process
• BIP 123 — BIP Classification
• BIP 9 — Version bits with timeout and delay
• BIP 8 — Version bits with lock-in by height
• BIP 90 — Buried Deployments
• BIP 50 — March 2013 Chain Fork Post-Mortem
• BIP 325 — Signet
• BIP 94 — Testnet 4

  BIP: 3
  Title: Updated BIP Process
  Authors: Murch <murch@murch.one>
  Status: Deployed
  Type: Process
  Assigned: 2025-01-09
  License: BSD-2-Clause
  Discussion: 2024-05-13: https://github.com/murchandamus/bips/pull/2
              2024-04-02: https://gnusha.org/pi/bitcoindev/59fa94cea6f70e02b1ce0da07ae230670730171c.camel@timruffing.de/#t
  Version: 1.4.0
  Requires: 123
  Replaces: 2