Kaspa’s blue score (often called blue score weight) is a numerical value that represents how much “blue work” lies behind a block. In simple terms, it tells the network how well-connected and honest a block is within the BlockDAG.
Kaspa does not use chain height like Bitcoin.
Instead, it uses blue score as its measure of cumulative work.
1. What Is the Blue Score?
The blue score of a block is the total number of blue blocks in the block’s selected parent chain, plus one for the block itself.
A blue block is a block considered part of the honest, well-connected part of the DAG (the “blue set”), as defined by GHOSTDAG.
Higher blue score = more accumulated honest work.
2. How Kaspa Calculates Blue Score Weight
The calculation is conceptually simple:
Blue Score = (Selected Parent’s Blue Score) + 1
But the selected parent is not chosen by height (like Bitcoin).
It is chosen as the block with the highest blue score among all parents.
So the algorithm is:
The selected parent is the block that:
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has the highest blue score
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belongs to the bluest, best-connected chain in the DAG
This ensures block ordering is stable even under high throughput.
3. Why Blue Score Is Important
Kaspa uses blue score instead of “longest chain” because it operates a DAG, not a chain.
Blue score is used to:
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choose the canonical ordering of blocks
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measure cumulative Proof-of-Work
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determine which chain is “heavier”
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resolve conflicts in the DAG
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help prevent attacks or reorganizations
It is Kaspa’s analogue to Bitcoin’s “total work”, but generalized for a multi-block-per-second DAG.
4. How Blue Score Weight Differs From Block Weight
In Kaspa:
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Block weight = measure used for ordering and consensus
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Blue score = cumulative count of blue blocks
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Blue work = PoW accumulated by the blue set
Blue score is the integer counter.
Blue work is the hash-based Proof-of-Work measure.
Block weight uses blue scores indirectly to determine ordering in GHOSTDAG.
5. Why Blue Score Works Well in Kaspa’s DAG
Because Kaspa produces multiple blocks per second, it must:
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include all valid blocks
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avoid orphaning
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preserve fairness
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maintain strong security
Blue score allows Kaspa to achieve:
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stable ordering
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low orphaning
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efficient consensus
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predictable finality
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scalable block throughput
It is one of the core innovations behind Kaspa’s architecture.
Kaspa calculates blue score weight by taking a block’s selected parent with the highest blue score and adding one. Blue score represents the number of “blue” (honest, well-connected) blocks in the DAG and serves as Kaspa’s measure of accumulated work and canonical ordering.