Abstract:
This comprehensive report documents 19 significant Bitcoin consensus rule changes (or 18, considering one accidental "failed" fork). Among these, three incidents led to identifiable chainsplits lasting approximately 51, 24, and 6 blocks in 2010, 2013, and 2015, respectively.
Terminology
| Term | Definition |
|---|---|
| Chainsplit | A blockchain divergence creating two separate chains with a shared ancestor. Can result from hardforks, softforks, or neither. |
| Hardfork | Loosens consensus rules, making previously invalid blocks valid. Requires node upgrades. |
| Softfork | Tightens consensus rules, making previously valid blocks invalid. Existing nodes may not need upgrades. |
(Origins traced to April 2012, formalized in BIP99/BIP123.)
List of Bitcoin Consensus Forks
| Date | Activation Block | BIP/Version | Description | Type | Outcome |
|---|---|---|---|---|---|
| 28 July 2010 | n/a | 0.3.5 | Disabled OP_RETURN to fix critical bug enabling arbitrary Bitcoin spends. | Softfork | Smooth upgrade, no issues. |
| 31 July 2010 | n/a | 0.3.6 | Disabled OP_VER/OP_VERIF; users advised to upgrade or shut down nodes. | Softfork | Minor upgrade challenges. |
| 15 Aug 2010 | 74,638 | 0.3.10 | Fixed 184.5B Bitcoin output overflow bug; 51-block chainsplit occurred. | Softfork | "Good" chain regained PoW lead post-fix. |
| 24 Mar 2013 | 227,835 | BIP34 | Required block height in coinbase transactions. | Softfork | 95% activation threshold, successful rollout. |
| 11 Mar 2013 | 225,430 | 0.8.0 | Unplanned LevelDB migration caused 24-block chainsplit; reverted to 0.7.2. | N/A | Double-spend occurred; original chain resumed lead. |
| 4 July 2015 | 363,731 | BIP66 | Enforced strict DER signatures; 6-block chainsplit due to unupgraded miners. | Softfork | Resolved after invalid blocks orphaned. |
| 24 Aug 2017 | 481,824 | BIP141/BIP147 | Segregated Witness (SegWit) upgrade. | Softfork | 95% versionbits signaling, successful activation. |
Key Insights
Was the 2013 Incident a Hardfork?
Debatable. The BDB lock limit increase (15 May 2013) relaxed consensus rules, technically qualifying as a hardfork. However, its non-deterministic nature led some to argue it wasn’t a "true" hardfork.
Chainsplit Incident of July 2015
During BIP66 activation, unupgraded miners built on an invalid block, causing a 6-block orphan chain. Highlighted risks of "false flagging" (signaling support without validating).
FAQs
Q: How many Bitcoin chainsplits have occurred?
A: Three major splits: in 2010 (51 blocks), 2013 (24 blocks), and 2015 (6 blocks).
Q: What’s the difference between hardforks and softforks?
A: Hardforks loosen rules (require upgrades); softforks tighten rules (may not require upgrades).
Q: Did SegWit cause a chainsplit?
A: No. Despite tensions, SegWit activated smoothly via softfork in 2017.
👉 Explore Bitcoin’s evolution further
Disclaimer:
While sourced meticulously, accuracy isn’t guaranteed. Corrections are welcome.
(Sources: BitMEX Research, GitHub, Bitcoin blockchain.)
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