ECIP 1091: Fork identifier (`forkid`) protocol fork list specification v2 Source

AuthorMr. Meows D. Bits
TypeStandards Track


EIP-2124 (forkid) and EIP-2364 (eth/64) propose discovery protocol modifications which depend on lists of fork values. In case these changes are adopted and implemented on Ethereum Classic networks, this ECIP defines canonical lists of forks numbers for inclusion in the generation and validation steps of these “ForkID” schemes.


This specification describes a set of forks which exclude TheDAO fork event block(s) from forkid calculations, as well as excluding all forthcoming blockNumber % 5000000 == 0 blocks that, according to the algorithmdescribed in ECIP-1017 and enabled on ETC Mainnet and some testnets, will see reduced block reward values.


Specify parameters for forkid generation and validation, so that in the case nodes on Ethereum Classic networks implement eth/64, they can do so in a consistent way.

As documented in EIP-2364, implementation for eth/64 does not demand consensus nor require any fork for node or network implementation.

Notwithstanding, it would be good for Ethereum Classic networks and clients to be able to implement the protocol change, if they want, according to a standard specification. Failure for clients to agree on forkid implementation could result in difficulty discovering each other.



Don’t include TheDAO fork blocks (eg. 1920000 on Mainnet, 1885000 on Morden) as a forkid parameter as specified in EIP-2124.

Don’t include any blocks subsequent and incidental to consensus-facing calculations according to accepted and implemented algorithms, eg. ECIP-1017.


The following data points are valid at time of last edit.

Ethereum Classic Mainnet (ETC)
  • Genesis Hash: 0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3
    • Forks: 1150000,2500000,3000000,5000000,5900000,8772000,9573000,10500839

  • Head Block Number FORK_HASH FORK_NEXT RLP Encoded (Hex)
  • | — | — | — | — |
  • head=0 FORK_HASH=fc64ec04 FORK_NEXT=1150000 c984fc64ec0483118c30
  • head=1149999 FORK_HASH=fc64ec04 FORK_NEXT=1150000 c984fc64ec0483118c30
  • head=1150000 FORK_HASH=97c2c34c FORK_NEXT=2500000 c98497c2c34c832625a0
  • head=1150001 FORK_HASH=97c2c34c FORK_NEXT=2500000 c98497c2c34c832625a0
  • head=2499999 FORK_HASH=97c2c34c FORK_NEXT=2500000 c98497c2c34c832625a0
  • head=2500000 FORK_HASH=db06803f FORK_NEXT=3000000 c984db06803f832dc6c0
  • head=2500001 FORK_HASH=db06803f FORK_NEXT=3000000 c984db06803f832dc6c0
  • head=2999999 FORK_HASH=db06803f FORK_NEXT=3000000 c984db06803f832dc6c0
  • head=3000000 FORK_HASH=aff4bed4 FORK_NEXT=5000000 c984aff4bed4834c4b40
  • head=3000001 FORK_HASH=aff4bed4 FORK_NEXT=5000000 c984aff4bed4834c4b40
  • head=4999999 FORK_HASH=aff4bed4 FORK_NEXT=5000000 c984aff4bed4834c4b40
  • head=5000000 FORK_HASH=f79a63c0 FORK_NEXT=5900000 c984f79a63c0835a06e0
  • head=5000001 FORK_HASH=f79a63c0 FORK_NEXT=5900000 c984f79a63c0835a06e0
  • head=5899999 FORK_HASH=f79a63c0 FORK_NEXT=5900000 c984f79a63c0835a06e0
  • head=5900000 FORK_HASH=744899d6 FORK_NEXT=8772000 c984744899d68385d9a0
  • head=5900001 FORK_HASH=744899d6 FORK_NEXT=8772000 c984744899d68385d9a0
  • head=8771999 FORK_HASH=744899d6 FORK_NEXT=8772000 c984744899d68385d9a0
  • head=8772000 FORK_HASH=518b59c6 FORK_NEXT=9573000 c984518b59c683921288
  • head=8772001 FORK_HASH=518b59c6 FORK_NEXT=9573000 c984518b59c683921288
  • head=9572999 FORK_HASH=518b59c6 FORK_NEXT=9573000 c984518b59c683921288
  • head=9573000 FORK_HASH=7ba22882 FORK_NEXT=10500839 c9847ba2288283a03ae7
  • head=9573001 FORK_HASH=7ba22882 FORK_NEXT=10500839 c9847ba2288283a03ae7
  • head=10500838 FORK_HASH=7ba22882 FORK_NEXT=10500839 c9847ba2288283a03ae7
  • head=10500839 FORK_HASH=9007bfcc FORK_NEXT=0 c6849007bfcc80
  • | head=10500840 | FORK_HASH=9007bfcc | FORK_NEXT=0 | c6849007bfcc80 |


  • Kotti


    • Genesis Hash: 0x14c2283285a88fe5fce9bf5c573ab03d6616695d717b12a127188bcacfc743c4
    • Forks: 716617,1705549,2200013

  • Head Block Number FORK_HASH FORK_NEXT RLP Encoded (Hex)
  • | — | — | — | — |
  • head=0 FORK_HASH=0550152e FORK_NEXT=716617 c9840550152e830aef49
  • head=716616 FORK_HASH=0550152e FORK_NEXT=716617 c9840550152e830aef49
  • head=716617 FORK_HASH=a3270822 FORK_NEXT=1705549 c984a3270822831a064d
  • head=716618 FORK_HASH=a3270822 FORK_NEXT=1705549 c984a3270822831a064d
  • head=1705548 FORK_HASH=a3270822 FORK_NEXT=1705549 c984a3270822831a064d
  • head=1705549 FORK_HASH=8f3698e0 FORK_NEXT=2200013 c9848f3698e0832191cd
  • head=1705550 FORK_HASH=8f3698e0 FORK_NEXT=2200013 c9848f3698e0832191cd
  • head=2200012 FORK_HASH=8f3698e0 FORK_NEXT=2200013 c9848f3698e0832191cd
  • head=2200013 FORK_HASH=6f402821 FORK_NEXT=0 c6846f40282180
  • | head=2200014 | FORK_HASH=6f402821 | FORK_NEXT=0 | c6846f40282180 |


  • Mordor


    • Genesis Hash: 0xa68ebde7932eccb177d38d55dcc6461a019dd795a681e59b5a3e4f3a7259a3f1
    • Forks: 301243,999983

  • Head Block Number FORK_HASH FORK_NEXT RLP Encoded (Hex)
  • | — | — | — | — |
  • head=0 FORK_HASH=175782aa FORK_NEXT=301243 c984175782aa830498bb
  • head=301242 FORK_HASH=175782aa FORK_NEXT=301243 c984175782aa830498bb
  • head=301243 FORK_HASH=604f6ee1 FORK_NEXT=999983 c984604f6ee1830f422f
  • head=301244 FORK_HASH=604f6ee1 FORK_NEXT=999983 c984604f6ee1830f422f
  • head=999982 FORK_HASH=604f6ee1 FORK_NEXT=999983 c984604f6ee1830f422f
  • head=999983 FORK_HASH=f42f5539 FORK_NEXT=0 c684f42f553980
  • | head=999984 | FORK_HASH=f42f5539 | FORK_NEXT=0 | c684f42f553980 |


  • Morden


    • Genesis Hash: 0x0cd786a2425d16f152c658316c423e6ce1181e15c3295826d7c9904cba9ce303
    • Forks: 494000,1783000,1915000,2000000,2300000,4729274,5000381

  • Head Block Number FORK_HASH FORK_NEXT RLP Encoded (Hex)
  • | — | — | — | — |
  • head=0 FORK_HASH=417adbe7 FORK_NEXT=494000 c984417adbe7830789b0
  • head=493999 FORK_HASH=417adbe7 FORK_NEXT=494000 c984417adbe7830789b0
  • head=494000 FORK_HASH=aeb67dfb FORK_NEXT=1783000 c984aeb67dfb831b34d8
  • head=494001 FORK_HASH=aeb67dfb FORK_NEXT=1783000 c984aeb67dfb831b34d8
  • head=1782999 FORK_HASH=aeb67dfb FORK_NEXT=1783000 c984aeb67dfb831b34d8
  • head=1783000 FORK_HASH=6a495281 FORK_NEXT=1915000 c9846a495281831d3878
  • head=1783001 FORK_HASH=6a495281 FORK_NEXT=1915000 c9846a495281831d3878
  • head=1914999 FORK_HASH=6a495281 FORK_NEXT=1915000 c9846a495281831d3878
  • head=1915000 FORK_HASH=e893e32d FORK_NEXT=2000000 c984e893e32d831e8480
  • head=1915001 FORK_HASH=e893e32d FORK_NEXT=2000000 c984e893e32d831e8480
  • head=1999999 FORK_HASH=e893e32d FORK_NEXT=2000000 c984e893e32d831e8480
  • head=2000000 FORK_HASH=12a0ac82 FORK_NEXT=2300000 c98412a0ac8283231860
  • head=2000001 FORK_HASH=12a0ac82 FORK_NEXT=2300000 c98412a0ac8283231860
  • head=2299999 FORK_HASH=12a0ac82 FORK_NEXT=2300000 c98412a0ac8283231860
  • head=2300000 FORK_HASH=02a93060 FORK_NEXT=4729274 c98402a93060834829ba
  • head=2300001 FORK_HASH=02a93060 FORK_NEXT=4729274 c98402a93060834829ba
  • head=4729273 FORK_HASH=02a93060 FORK_NEXT=4729274 c98402a93060834829ba
  • head=4729274 FORK_HASH=4802d0c7 FORK_NEXT=5000381 c9844802d0c7834c4cbd
  • head=4729275 FORK_HASH=4802d0c7 FORK_NEXT=5000381 c9844802d0c7834c4cbd
  • head=5000380 FORK_HASH=4802d0c7 FORK_NEXT=5000381 c9844802d0c7834c4cbd
  • head=5000381 FORK_HASH=0b559b1d FORK_NEXT=0 c6840b559b1d80
  • | head=5000382 | FORK_HASH=0b559b1d | FORK_NEXT=0 | c6840b559b1d80 |


The Ethereum Classic consensus protocol did not fork at block 1920000.

The Ethereum Classic disinflationary monetary policy is not considered a series of forks, it is the natural “stepping” behavior of a deterministic algorithm.


Respective reference implementations for forkid generation are documented in EIP-2124 and EIP-2364.

At the time of last edit, client implementation tests may be found at:

  • Core-Geth:,
  • Multi-Geth:
  • OpenEthereum:

Change Log

  • 2020-06-03
    • Modify Kotti eligible fork specs, removing blocks 2M and 5M. Prior specifications were generated using a faulty chain configuration, which wrongly included these blocks. Rel
      • This modification is the first of its kind within this document, and is the sole modification against the superseded ECIP1082.