Wiki / Forks / Bitcoin Unlimited

Bitcoin Unlimited

From the Bitcoin Takeover Wiki · ✓ 4 sources · 2 podcast anchors · built 2026-11-13

A full-node client that let users and miners choose their own block size limit, governed by a voting federation; later a Bitcoin Cash implementation.

◆ Takeover vieweditorial · opinion, labelled

The wiki's angle: Unlimited was the most explicitly political client of the war, with a written constitution that put hashpower votes at the centre.[1]

Contents

  1. Principle
  2. How it differs
  3. March 2017 attack
  4. Bitcoin Cash era
  5. Heard on Bitcoin Takeover
  6. References

Principle

The Articles of Federation assert that “Bitcoin is and should be whatever its users define by the code they run and the rules they vote for with their hash power”[1]. They describe a federation with a publicly identified President and Secretary who handle Bitcoin Unlimited Improvement Proposals (BUIPs)[1].

How it differs

Bitcoin Core had a hard-coded one-megabyte limit; Bitcoin Unlimited instead let users signal the limit they prefer and automatically track the chain with the most proof of work, regardless of block size[2]. It followed Bitcoin XT and Bitcoin Classic as an alternative path to larger blocks[2].

March 2017 attack

Bitcoin Unlimited nodes were attacked after a bug was disclosed on 14 March 2017, and the number of nodes fell from about 780 to about 370 before recovering within 24 hours, according to coin.dance data cited by Wikipedia[2].

Bitcoin Cash era

From version 1.1.0.0, Bitcoin Unlimited releases are compatible with Bitcoin Cash[2]. On S17 E19, Amaury Séchet credited the CashTokens upgrade to Bitcoin Unlimited's push and said some of its developers later moved to a coin called Nexa[3].

Heard on Bitcoin Takeover

On S16 E30 (June 2025), Peter Rizun contrasted the earlier proposals with BU: “XT and classic were both attempts to reach consensus so we could all move forward together and guarantee there would be no fork.” By contrast, he said, “Bitcoin Unlimited was an attempt to say, OK, well, we're going to give up.”[4]

References

  1. primaryBitcoin Unlimited, “Articles of Federation” (PDF) [archived]
  2. secondaryWikipedia, “Bitcoin Unlimited” [archived]
  3. episodeS17 E19: Amaury Séchet on CashTokens as Bitcoin Unlimited's idea▶ listen at 2:27:17timestamp transcript-derived, pending a listen [archived]
  4. episodeS16 E30: Peter Rizun on what Bitcoin Unlimited was trying to show▶ listen at 1:19:19timestamp transcript-derived, pending a listen [archived]

Related

Bitcoin XT
Mike Hearn's fork of Bitcoin Core that shipped BIP-101 in August 2015 and opened the public, client-versus-cli
Bitcoin Classic
The early-2016 client that proposed a one-time 2 MB hard fork (BIP-109) after Bitcoin XT stalled.
Bitcoin Cash
The big-block fork of 1 August 2017, Bitcoin's first durable chain split.
Block size war
The 2015–2017 fight over Bitcoin's 1 MB limit that produced the first durable chain split.
Categories: Forks · Fork lineage
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