Solo mining in a browser tab. The block is built and checked by the tab's own node from its own validated mempool, hashed in the tab, and handed to the chain. Testnet's twenty-minute rule makes it real: twenty minutes after the last block, the next one may be mined at the lowest difficulty, and a laptop finds one of those in about a minute.
Live: https://bitcoin-blake.github.io/winch/
One page over blaketestnode's browser node, through the same loader Reef and Bight use (browser/tabnode.js, pinned by commit). The tab fetches the fork-point UTXO snapshot of txbt4 (the BLAKE2b testnet4), checks its hashes, validates every block since the fork, follows the chain tip and keeps its own mempool.
- The block. The node worker builds the next block from the tab's chain tip and mempool (datstr SPEC 6.3, without a pool): coinbase paying this tab's script, witness commitment, merkle root, a v2 header with the difficulty the chain's rules expect for the block's time. Every block rule the worker knows is run on it before it is handed out.
- The window. The header's bits say whether the twenty-minute window is open. Outside it the tab waits, with a countdown on screen read from the last block's time in its own chain. A block may be dated up to two hours ahead, and the rule looks at the block's own time, so by default the tab asks for the window's block dated to the boundary fifteen seconds before it and hashes into the window; the estate's own gateways take the boundary in the same second, so a tab that waits for the clock never wins. A setting sets the lead, or 0 to wait for the clock; another allows hashing at full difficulty outside the window, for tests.
- Hashing. The datstr browser miner's loop, BLAKE2b in WebAssembly (about 40× the JavaScript loop), one worker per core, rolling the nonce over the 80-byte work. A nonce that meets the target goes back to the node worker, which assembles the full block and checks the hash against the network target.
- Handing it over. A tab has no peer-to-peer connection, so the block is published as a kind 23405 event (content the block hex, tagged with the chain). A node that follows that kind runs
submitblock; the estate's mempool publisher does. The tab does not take anyone's word for the result: it sees its block when its own chain tip moves to it, or sees which block won instead. - Rewards pay Reef's wallet when this browser has one (same origin, same storage), else a key Winch makes and keeps; a coinbase on this chain matures after 6,705 blocks.
Measured on the estate's workstation: 12 workers, about 85 MH/s, about 50 s per block on average at difficulty 1.
A winch hauls a line in. Reef is the knot, Bight the slack, Winch the pull.
AGPL-3.0-or-later.