The lecture in one paragraph
In a single-chain protocol, two miners who find a block at the same moment produce a conflict, and the protocol resolves it by discarding one. That is an orphan. It is tolerable at ten-minute intervals because almost every miner has seen the previous block before finding the next one. Speed the chain up and collisions become common, orphan rates climb, and the work being thrown away is exactly the work that was securing the ledger. This is why “just make the blocks faster” was considered a dead end for two decades.
Kaspa keeps the blocks. Instead of a chain, blocks reference multiple parents and form a directed acyclic graph — a blockDAG. The consensus protocol, GHOSTDAG, then derives a single total order over every block in that graph, and every honest node derives the same order. Nothing is discarded, so raising the block rate no longer costs security. Mainnet has run at ten blocks per second, one block every 100 milliseconds, since the Crescendo hardfork on 5 May 2025.
Blue, red, and the thing everyone gets wrong
GHOSTDAG colours blocks. A block is blue when its anticone — the set of blocks that neither reference it nor are referenced by it — is narrower than the parameter k. Otherwise it is red.
Red does not mean rejected. A red block is stored, it is ordered, and its transactions settle normally. What red costs the block is its security weight and its reward. If you remember one correction from this course, make it that one: nothing in Kaspa is discarded for arriving at the same time as something else.
Confirmation is not finality
Your transaction is confirmed once it is included in a block and GHOSTDAG has fixed its place in the order — about a second on mainnet. It is not final in the sense of being impossible to reverse, because on any proof-of-work network finality is probabilistic: it grows as work accumulates behind your transaction and never technically completes.
Both directions of this confusion are dishonest. Comparing Kaspa’s confirmation time to another chain’s finality flatters Kaspa; comparing its probabilistic finality to a proof-of-stake chain’s deterministic finality without saying they are different guarantees flatters the other chain. Name the measurement you mean.
Where the coins come from
There was no premine, no presale and no foundation allocation. Every KAS in existence was mined, starting November 2021, and the early block history is public if you want to check rather than take this page’s word for it. Since May 2022 the network has been in its chromatic phase: the block reward is multiplied by 2^(-1/12) every Kaspa month, and twelve of those steps compound to exactly one half. The result is an annual halving with no cliff and no miner revenue shock — and because 2^(-1/12) is the ratio between two semitones, and the opening rate was 440 KAS per second, the schedule is literally built on the twelve-tone musical scale.