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Blocks and Headers

🧱 Primitive

Type: PrimitiveDifficulty: 1/4blocks-and-headersVerified: 2026-02-12

Summary

Block Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. commit to previous history and transaction set metadata, making tampering detectable and costly to rewrite.

Story

A Full NodeSoftware that independently validates blocks and transactions against consensus rules. receives a new block and must decide quickly: accept or reject. It starts with the header. The header contains the previous block hash, timestamp, difficulty target, nonce, and merkle root commitment. This tiny structure links every block to prior history and anchors Proof-of-WorkConsensus mechanism where miners expend hashpower to find valid blocks below the target threshold.. If any transaction in the block changes, the merkle root changes; if any parent changes, the previous-hash link breaks. This chaining is why users can verify integrity without trusting a central archive. Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. also enable lightweight clients to track chainwork and detect reorganizations. In practice, blocks and Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. are the protocol’s compact security boundary: enough data to enforce ordering and commitment, then full transactions for detailed validation.

Deep Dive

Header fields

  • prevhash links parent history and defines chain continuity.
  • Merkle root commits to included transaction set.
  • nBits encodes difficulty target for Proof-of-WorkConsensus mechanism where miners expend hashpower to find valid blocks below the target threshold. validity.

Security properties

  • Changing historical content requires recomputing Proof-of-WorkConsensus mechanism where miners expend hashpower to find valid blocks below the target threshold. for affected blocks.
  • Header-only validation can quickly reject obviously invalid branches.
  • Propagation latency can still cause short-lived stale block races.

Real Data

Tip Height

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Reference height for exploring recent headers and block intervals.

Hashrate

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Approximate global hashpower securing the header chain.

Key Takeaways

  • Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. are compact commitments to block state and ancestry.
  • Merkle commitments make transaction tampering evident.
  • Chain integrity is hash-linked and work-backed.

Security Notes

  • Header chain selection follows cumulative work, not longest by count.
  • Short stale races are normal; deep unexpected reorgs are security events.

Node Security Panel

Vulnerabilities (0)

    Attacks (1)

    Assumptions (0)

      Policy vs Consensus (1)

      Policy vs Consensus

      Consensus RulesNetwork-wide validation rules every full node enforces to determine valid blocks and transactions. defines header validity and chain selection by work; policy affects relay strategy and temporary buffering behavior.

      Consensus Rules

      • ConsensusHeader hash must satisfy target encoded by nBits.
      • ConsensusHeader must correctly reference previous accepted block hash.

      Policy Rules

      • PolicyHeader relay and orphan handling can vary by implementation policy.
      • PolicyFull NodeSoftware that independently validates blocks and transactions against consensus rules. policy may prioritize certain peer sources under bandwidth pressure.

      Security Research Panel

      2013 BerkeleyDB Fork Event

      2013

      Client-version incompatibility caused temporary chain divergence despite valid-looking Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. on each side.

      Explorer Deep Links

      Some sources are external. When an internal Raw Block view is available, we'll surface it here.

      Claim Sources

      Each block header commits to prior history and transaction merkle root.

      Chain selection uses cumulative work.

      Claim Registry Links

      • Each Block HeaderCompact block metadata containing previous hash, merkle root, timestamp, nBits, nonce, and version. commits to the previous block hash, linking blocks into a tamper-evident chain.

        Verified: 2026-02-12

        Source

      Further Reading

      Graph Neighbors

      DirectionRelationNode
      OutgoingDEPENDS_ONMining and Subsidy
      IncomingDEPENDS_ONUTXO Model

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