Glossary · Toccata 101

address

Spells out the lock an output will carry. It holds nothing. A q address carries a public key, a p address carries the fingerprint of a script.

block

A batch of transactions sealed by a miner's proof of work. Kaspa makes ten a second.

blockDAG

Kaspa's ledger: blocks made in parallel, each pointing at several earlier blocks, a web rather than a line.

block timestamp

The wall clock time a miner writes into the block it makes. The network only checks that it is not too far ahead and not older than the recent blocks.

blue block

A merged block that was well connected when it arrived, counted in the order and paid. Nearly every block is blue.

blue score

A block's count of the blocks the network agrees came before it. The gap between the newest block's count and an older block's is how many blocks sit on top of that one.

blue work

The proof of work piled up behind a block, counting blue blocks only. The rule that picks the chain compares it.

byte

The unit data is counted in: eight bits, about one character of text. A key is 32 bytes, a plain transaction a few hundred.

chain block

A block the network's ordering puts on the main line. It merges the blocks around it, accepts their transactions once and pays their miners in its coinbase.

change

An output that comes back to the sender's own address: what's left from the inputs after the payment and the fee.

checksum

The last eight characters of an address, computed from the rest, so a typo is caught before any coin moves.

coin age

How far the network's DAA score has climbed since the block that made a particular coin. Every coin carries its own.

coinbase

The first transaction of a block, made by the miner, with no inputs. It pays the rewards for the blocks that block merges: subsidy plus fees.

confirmation

One block on top of the block that accepted your transaction. The reference wallet waits for 100 of them, about ten seconds.

covenant

A UTXO locked by a program that inspects the transaction spending it and can refuse it.

Crescendo

The Kaspa upgrade of May 2025 that raised the network to ten blocks per second and added the first, narrow introspection opcodes (KIP-10).

DAA score

Kaspa's counter of accumulated work, used as the network's clock for locks and activations.

DAG

Directed Acyclic Graph: a set of items where each one points back at earlier ones, and no path of those pointers ever leads back to where it started.

difficulty

How many hashing attempts a block takes on average. It adjusts so the network keeps making ten blocks a second.

ECDSA address

The rarer kind of q address, carrying a 33-byte ECDSA key. A spend must show an ECDSA signature by that key.

explorer

A website that shows the chain: blocks, transactions, addresses and their UTXOs.

fee

Input minus output, goes to the miner who placed the transaction inside a block in the network.

fee rate

A transaction's fee divided by its mass, in sompi per gram. Miners fill their blocks with the transactions that pay the most per gram.

finality

The depth past which a node will not undo a block, whatever it hears: 432,000 blocks, twelve hours.

fingerprint

The hash of a script, 32 bytes, the part a p address carries. From the fingerprint alone the script cannot be read.

GHOSTDAG

The rule that turns the blockDAG into one order: pick the chain by blue work, colour the merged blocks blue or red, sort them.

gram

The unit a transaction's mass is counted in. The fee is a price per gram.

hardfork

A change to Kaspa's rules that every node must adopt. It activates at a fixed DAA score and carries a name (Crescendo, Toccata).

hash

A fixed-size fingerprint computed from any data. Change one byte of the data and the hash changes completely.

input

An existing UTXO from a past transaction, ready to be used.

introspection

A script's ability to read the transaction it is part of: inputs, outputs, amounts, addresses. Narrow since Crescendo, full since Toccata.

KAS

Kaspa's coin. 1 KAS is 100,000,000 sompi.

key lock

The lock a q address stands for: this key must sign. Whoever holds the matching private key can spend.

KIP

A Kaspa Improvement Proposal, a change to the network's rules.

KRC-20

A token convention that writes a note into a transaction for an off-chain program (an indexer) to read. The node itself skips the note.

Layer 1 (L1)

The Kaspa network itself, as opposed to anything built on top of it. A covenant runs on L1, checked by every node.

lock

What an output carries besides its amount: the script that decides what a spending transaction must show. Its technical name is the script public key.

mainnet

The real Kaspa network, where KAS has value. Its addresses start with kaspa:, test network addresses with kaspatest:.

mass

A transaction's weight in grams, what the fee is priced by: a size weight and a storage weight, the heavier one counts.

mempool

A node's waiting room: the transactions it has checked and holds until a miner puts them in a block.

merge set

The blocks a chain block brings into the order: everything in its past that the previous chain block had not covered.

miner

A node that orders accepted transactions into blocks by proof of work, and collects the fees.

node

A computer running Kaspa that checks every transaction against the rules and keeps the set of UTXOs.

nonce

The number a miner changes between hashing attempts until the block's hash falls under the target.

opcode

One instruction of Kaspa script, one byte, such as OpCheckSig.

output

A piece of KAS created by a transaction, with an amount and a lock.

p address

An address that starts with p. It carries the fingerprint of a script, and a spend must show the script itself.

parent

An earlier block a new block points at. A Kaspa block points at every tip its miner saw, so it has several.

past median time

The middle value of the times written on the recent blocks. A new block has to be later than it, so network time never moves backwards.

peer

Another node this node talks to. Nodes announce transactions and blocks to their peers, and every peer checks for itself.

piece

The word cards 1.1 to 1.3 use for a UTXO.

private key

The secret a wallet keeps (the seed makes it). Whoever holds it can spend what its public key locks.

proof of work (PoW)

The computation a miner must do to make a block valid. It is what makes Kaspa's history costly to rewrite and reorganize.

public key

The key an address is made from, safe to show. Only the matching private key can make a signature it accepts.

q address

An address that starts with q. It carries a public key, and a spend must show that key's signature.

red block

A merged block that arrived too late for its neighbours. Kept, its transactions still count, but its miner is paid nothing for it.

redeem script

For a p address, the script the spender reveals when spending. The node hashes it, matches the hash to the address, then runs it.

Schnorr key

The usual kind of key in a q address, 32 bytes. A spend must show a Schnorr signature by that key.

script

The small program every output carries, run by every node when the output is spent.

script lock

The lock a p address stands for: show the script that matches the fingerprint, then satisfy it. Every covenant lives behind one.

script public key

The lock on an output: a small program attached to the UTXO that determines what a spending transaction must show, for a normal wallet the signature of a key.

selected parent

Of a block's parents, the one with the most work behind it. Following selected parents from the newest block gives the chain.

signature

A proof, made with the spender's private key (seed), that authorizes using a UTXO.

signature script

The half of the program the spender brings, carried by the input. It may only put data on the stack, it cannot compute.

size weight

The weight of a transaction's bytes and checking work (compute mass), about two thousand grams for a plain payment, the same whatever the amounts.

sompi

The unit amounts are counted in. 1 KAS is 100,000,000 sompi.

spend

To use a UTXO as an input. The UTXO is consumed and its amount moves into the new outputs.

stack

The small pile of values a script runs on. An instruction takes what it needs off the top and puts its result back. At most 244 items at any moment.

storage weight

The weight of the new pieces a transaction creates (storage mass): about 10¹² divided by each piece's value in sompi, minus a relief for the pieces it spends. Small pieces are heavy, and past 500,000 grams no block can hold the transaction.

subsidy

The new KAS a block brings into existence, set by the rules for its DAA score and shrinking over the years.

target

The bar a block's hash must fall under. The lower the target, the more attempts a block takes.

tip

A block no other block points at yet. The next block will point at the tips its miner sees.

Toccata

The Kaspa upgrade, active on mainnet since 30 June 2026. Made the rules a transaction can carry general: a program that reads the whole transaction, keeps memory between spends and carries an identity.

transaction

Spends existing UTXOs (its inputs) and creates brand-new ones (its outputs), accepted or refused by every node as a whole.

Unix time

How computers store a moment: the number of seconds, or milliseconds, since the start of 1 January 1970.

UTXO

Unspent transaction output. A piece of KAS created by an earlier transaction and not yet spent, with its own amount and its own lock. A balance is the sum of them.

UTXO set

Every unspent output on the network, kept by each node. A transaction's inputs must be in it, and each block moves pieces out of it and new ones into it.

version byte

The first byte inside a decoded address: 0 for a Schnorr key, 1 for an ECDSA key, 8 for a script fingerprint.

wallet

The software that keeps your keys, adds up the UTXOs they can unlock, and builds and signs your transactions.