Grin v3.0.0 Hard Fork upgrade (Jan 2020)

This post will be updated as there is progress, with an announcement in the comments section each time there’s a significant change.

Version 0.5
November 26 2019

Important Block Heights and Dates

Event Date or Block
Testnet Hard Fork Block Height 298,080
Testnet Hard Fork Date (expected) 2019-12-19
Hard Fork Block Height 524,160
Hard Fork Date (expected) 2020-01-15 (est.)


As previously announced, Grin is making network wide upgrades through four scheduled hard forks in the first two years after launch. These are set in the code to occur in rough intervals of 6 months, at every 60*24*7*26 = 262,080 blocks:

  • Hard Fork 1: 262,080 Completed successfuly
  • Hard Fork 2: 524,160
  • Hard Fork 3: 786,240
  • Hard Fork 4: 1,048,320.

The second network upgrade is expected to happen in mid-January 2020. Compatible versions of grin node, grin-wallet, and grin-miner will be versioned 3.0.0 or greater. The first releases of these are scheduled for December.

This post describes breaking changes, timeline and communications that will take place, with the intention that the upgrade goes as smoothly as possible and that ecosystem participants can make the necessary preparations. It will be updated as necessary with additional information once available.

Important Information:

Grin v3.0.0 is a network wide upgrade. Apart from updating their binaries in order to transact after the upgrade, users are not required to do anything. Stored grins will not be affected. Beware of scams telling you to move your coins elsewhere.

Breaking Changes

The following is an incomplete list of breaking changes. This section will be updated as required until scope has been finalized.


  • New secondary proof-of-work. Grin remains true to its commitment to tweak CuckARoo as part of every upgrade in order to discourage manufacturers from building specialized ASIC hardware for it. As such, Cuckarood29 will be deprecated for a new algorithm, its details yet to be announced. There will be a forum post defining the algorithm in advance, alongside corresponding pull requests. Mining software must upgrade their solver.
    • Definition: To be announced.
    • Cuckoo Cycle repository:
    • Corresponding Grin HF PoW PR: To be announced.
    • Grin-miner pull request: To be announced.


To be confirmed.


To be confirmed.

Actions Required

To be confirmed.

Detailed contents & Status

For the latest details and status of individual items, please refer to the v3.0.0 planning issue on /grin-pm.


Date Milestone Description
2019-10-31 Scope freeze New functionality, improvements, and fixes targeted for the upgrade are defined and communicated
2019-11-29 PoW Release New secondary proof of work is released along with a basic solver.
2019-12-03 Beta Binaries Release Release of grin, grin-wallet, grin-miner beta binaries.
2019-12-12 Code Freeze No changes are permitted on the branch to be released except critical bugs.
2019-12-13 Release candidate binaries Release of grin, grin-wallet, grin-miner binaries.
2019-12-19 Floonet upgrade Launch of Floonet hard fork and public testing.
2020-01-15 Mainnet upgrade Grin is forking to v3.0.0.

NB: Actual dates (but not the hard fork block height) may vary slightly based on the current circumstances.


Prior to the hard fork, the Grin community will communicate with the following medium:

Date Milestone Description
2019-12-01 Communication to exchanges and mining pools Communicate with exchanges and mining pools to make sure everyone is aware and are getting ready for the upgrade, offering assistance as required.
2019-12-15 1st Banner First banner on the website with a link to a summary of what will happen.
TBC 2nd Banner Update banner on the website with binaries and urge ecosystem to upgrade.
2020-01-08 Final banner Update banner to urge mining pool and exchanges to upgrade.
Immediately following upgrade v3.0.0 banner Add a banner on the website informing about the hard fork, the changes introduced, and links to the latest binaries.


For any feedback, questions, concerns, or problems, please contact Daniel Lehnberg:


Great keep moving :+1:


On and on! Let it be so!

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அதற்கு பதிலாக நீங்கள் ஆங்கிலத்தைப் பயன்படுத்துகிறீர்கள் எனில், உங்களுக்காக மூடிய உமிழ்வுடன் ஒரு கிரின் ஃபோர்க் செய்வேன்


Happy very happy to see Tamil language but just wanted to know why when very few can understand ?


A mockery of the people who write in Chinese instead of English.

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Please note that the post above has been updated with timelines and more details, as was discussed in the Nov 12 development meeting.

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Thanks. Looks like the OP still has some broken links to old website: edited by mod, by the way. That should now be

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Thanks @chronos, fixed

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If i have some Grin in Ironbelly wallet, and if Ironbelly dont update according with hardfork, what is happent ?

Short answer: Nothing will happen. Your grins are safe.

Longer answer: You might have problems using Ironbelly after the hard fork if it is not v3.0.0 compatible (although I’m sure it will be). Nevertheless, if you have backed up your seed / mnemonic words, you could restore to a v3.0.0 compatible wallet and use your grins there instead.

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Hi I would like to know apart from GMiner and lolMiner, are there any other miners available for use after the fork???
PS: I am personally running some test. That’s why the question. :slight_smile:

I can’t say anything on other miners, but Kryptex Pro has been updated today, and it mines very slick imo

Happy New Grin! :dizzy: :tada: :fireworks:


config: ubuntu 16.04, i5-3230m

Just changed my 2.x grin binary with latest 3.x:


Invalid instruction (core dump)

Right now deleted all the blockchain data and it started to sync.
Will see if sync process will end with success.

UPDATE 1: Just recompiled the grin binary from git source and now it starts without any problem and no need to delete the previous blockchain data, it continues to sync :slight_smile:

UPDATE 2: Blockchain sync finished successfully.

Devs, please compile grin for github with optimizations for earlier processors (mine is i5-3230m).

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