Plan To Support Bitcoin's Segwit2X Hard Fork? Here's A Readiness Checklist

10/30/2017 - 18:39 UTC
Plan To Support Bitcoin's Segwit2X Hard Fork? Here's A Readiness Checklist

In sixteen days from now, on November 16, approximately 90 days after Segregated Witness was finally activated in the Bitcoin blockchain, a block larger than 1MB will be generated by bitcoin miners. This will be done at block height 494,784. At that moment, the Segwit2X hard fork will occur, aiming to increase Bitcoin’s capacity.

If you are a casual bitcoin user, the upgrade will be seamless, and no action is required from you. But if you are a bitcoin node operator, interested in participating in the upcoming hard fork and be compatible with the larger blocks, here is a readiness checklist.

if (block_height ≥ 494,784) max_block_size = 2 MB

SPV Wallets

If you run or depend on an SPV wallet, fear not. Because an SPV wallet downloads only block headers and transactions relevant to the wallet’s owner, it doesn’t give a damn about block size limit. Thus the S2X hard fork will be invisible to all SPV wallets, and they are expected to continue working without any change at all.

BTC1 nodes

The BTC1 client was specifically designed to implement the upgrade requirements automatically.

Thus, if you run your node on the BTC1 client, no action is required from you. In fact, the Segwit2X project actively recommends running the BTC1 client during the hard fork.

Bitcoin Unlimited nodes

Nodes running Bitcoin Unlimited (BU) don’t need to do anything also.

The BU client is configured by default to accept blocks up to 16 MB in size which is higher than the new maximum size of blocks that miners will produce (2 MB). Thus the hard fork will be seamless and invisible to all BU nodes.

The situation is different for bitcoin miners running BU software. The hard fork will not be invisible to them. Instead, they need to configure their nodes to accept 2MB blocks from 494,784 onward. Also, they need to make sure that the size of block 494,784 will be greater than 1,000,000 bytes.  

Other Bitcoin clients

If you run a bitcoin client, that does not fall in any of the above categories; you will need to tweak two constants to remain compatible with the larger blocks in the B2X blockchain.

For SegWit-compatible clients you will need to set:

  • Maximum block weight from 4,000,000 to 8,000,000
  • Sig-ops per block from 80,000 to 160,000

For non-SegWit-capable clients you will need to set:

  • Maximum base block size from 1,000,000 to 2,000,000
  • Sig-ops per block from 20,000 to 40,000

Both types of clients should add new DNS seeds:

  • BitPay:
  • OB1:
  • Blockchain:
  • Bloq:



Disclaimer: This article should not be taken as, and is not intended to provide, investment advice on Bitcoin, Cryptocurrencies or finance in general.