What BTC BLAKE2b is.

Fork height

961,640

Activated

30 Aug 2026

Proof of work

BLAKE2b

Node software

Bitcoin Knots

Bitcoin proves a block by hashing its header twice with SHA-256 until the result falls below a target. This chain replaces that with BLAKE2b over a restructured 164-byte header. The rules that matter to a holder — the 21 million limit, the halving schedule, the addresses, the signatures — are untouched. What changed is who can compete to produce blocks.

SHA-256 mining has been the preserve of purpose-built machines for over a decade, because the function is cheap in silicon and ruinously expensive everywhere else. BLAKE2b moves that line. It is fast enough on an ordinary processor that a laptop can produce valid work — not competitively against a warehouse, but genuinely, and measurably: one core computes about 6.66 million BLAKE2b hashes a second.

There is a second, temporary change. Blocks are capped at 800,000 weight units instead of the usual 4,000,000, a restriction that expires on 1 September 2027. It is why blocks on this chain are smaller than you might expect.

This is not the SHA-256 chain. Bitcoin mainnet carried on with SHA-256 and is entirely unaffected by any of this. From block 961,640 there are two chains that share one past, and a coin on one is not a coin on the other.

Because the history is shared, an address that held BTC before the fork exists on both chains. That is exactly why you should never point mining payouts, or anything else, at an address holding SHA-256 BTC. Create a fresh wallet for this chain and use an address that has only ever existed here. It costs nothing and it removes a whole category of mistake.

Two things follow from the algorithm. The first is that Sia-generation ASICs — built for BLAKE2b when Siacoin used it — mine this chain on stock firmware, with no reflash and no patched software. The second is that SHA-256 ASICs cannot mine it at all; an Antminer S19 will connect, look busy, and have every share rejected. Which machines work, and how often each lands a share, is set out on the hardware page.

Mining needs three values and no account: a stratum URL, your payout address as the worker name, and any password. On this pool the address is the account — there is nothing to register and no password to lose.

1. 01

   A fresh address

   Create a wallet for this chain and copy a receiving address. Never reuse one that holds coins on the other side of the split.

2. 02

   The port for your hardware

   3333 for a BLAKE2b ASIC, 4444 for an FPGA or GPU, 5555 for a CPU. Add one to each for solo mining.

3. 03

   Three fields

   URL, worker, password — then watch for accepted shares. Your page appears under Miners within a minute or two.

The setup page has the exact values, and the published protocol specification has the wire format down to the byte if you are writing a miner yourself.

Is this the same as SHA-256 Bitcoin?

No. They share every block before 961,640 and nothing after it. Bitcoin mainnet continues with SHA-256; this one runs separately, with its own difficulty, blocks and coins.

Why change the proof of work at all?

To move mining back within reach of general hardware. BLAKE2b is cheap enough on a normal processor that a computer can produce valid work, which SHA-256 has not allowed for years.

Do I need a new wallet?

Yes, and it matters. Use an address created for this chain only. An address that holds BTC exists on both chains, and mixing them is how people lose coins.

What software does the node run?

Bitcoin Knots, from version 29.4.1 onwards. A node has to be one that follows the fork; an unmodified Bitcoin Core node stays on the SHA-256 chain and will not see this chain's blocks as valid.

Where can I read the specification?

For the chain itself, bitcoin-blake2b.org. For the mining protocol as this pool speaks it — every field, its length and its byte order, with a reference implementation and a test vector — see stratum-protocol.md.