§ 11 · Blockchain · Overview
Blockchain
One chain of blocks that every node agrees on
On this page 5 sections
A blockchainBlockchain: The ledger itself: a chain of blocks, each holding a batch of transactions and pointing to the block before it by its hash. Changing an old block breaks every link after it. is what you get when every block points back at the one before it. Pearl’s started on 27 April 2026 with the genesis blockGenesis block: Block 0, written into the software rather than mined. Pearl's is dated 27 April 2026, pays no reward, and quotes a Bitcoin block hash to show it wasn't made earlier., and a new block has been added roughly every three minutes since.
The point of the chain is agreement. Many nodes, run by strangers, each keep their own copy, and they all end up with the same one. This group explains how: what links the blocks, how they are numbered, what nodes do when the chain splits, and the few places where the rules themselves changed.
Try it
A short chain of blocks, each linked to the one before by its hash. Change a block and watch every block after it break.
What makes it a chain?
Every 108-byte header begins, after its version, with the 32-byte hash of its parent’s header. And a block’s hash covers its whole header, which in turn commits to the block’s transactions (through the Merkle root) and its mining proof (through the proof commitment).
So changing anything in an old block changes its hash, which breaks its child’s link, which changes the child’s hash, and so on to the tip. Rewriting history means redoing the mining work for every block from that point on. The bytes are on previous block.
| Field | Bytes | Value |
|---|---|---|
| Version header.version | 4 @0 | 0x20000000 int32 LE. BIP-9 style 0x20000000 since block 1; no consensus meaning in Pearl. |
| Previous block header.prevBlock | 32 @4 | eb555c52c695cfa0b2ad27f0d1f96ca55f1dc32d864e13218b4bd9041b969c99 Hash of the parent block, stored byte-reversed; shown in display order. |
| Merkle root header.merkleRoot | 32 @36 | c6c21c0c4204b9f39e17d7f79811aff53eac88ea0d80fcdeffdad96ba3fa8963 Root of the SHA256d Merkle tree of this block’s txids, stored byte-reversed. |
| Time header.timestamp | 4 @68 | 1792513562 (2026-10-20 16:26:02 UTC) uint32 LE Unix seconds. Must be at least 1 s after the parent and at most 5 min in the future. |
| Bits header.bits | 4 @72 | 0x176af3a6 Compact target. Difficulty 40157376.49334089. The certificate's jackpot hash (not this header's hash) must meet it. |
| Proof commitment header.proofCommitment | 32 @76 | 49e67ac73638201f2815a24689b8b1df672f9176df2ee232b00c1632fda3524d SHA256d(LE32(certificate version) ‖ public data). Replaces Bitcoin’s nonce: Pearl headers have no nonce. |
How do nodes agree on one chain?
Three rules do the work, each with its own page:
- Most work wins. If two miners extend the chain at almost the same moment, nodes follow the branch with more total work. Pearl only switches when the new branch leads by at least a quarter of a block’s work. See the most-work chain.
- Old history is pinned. Every 10,000 blocks, a block hash is written into the software. Nodes refuse chains that disagree with these checkpointsCheckpoint: A block hash built into the node software at a fixed height. Pearl has one every 10,000 blocks so far, and nodes refuse any chain that disagrees with them., and won’t reorganize below the last one. See checkpoints.
- Rule changes happen at fixed heights. Everyone’s software knows in advance the block where a new rule starts. See forks and upgrades.
What are the landmarks so far?
- Genesis block
- height 0
- 2026-04-27 09:00:00 UTC
- Block 1
- 3,229.64 PRL
- the first reward, one second later
- Hard forks
- 71,935 · 99,000
- Soft forks
- 91,630 · 96,251
- Latest checkpoint
- 120,000
- one every 10,000 blocks
- Snapshot tip
- 130,827
- 20 October 2026
The tip right now is block 130,827.
| Height | Date | What happened |
|---|---|---|
| 0 | 2026-04-27 | Genesis: no reward, and a message quoting Bitcoin block 946,842 |
| 1 to 5 | 2026-04-27 | Mined exactly one second apart, at difficulty 1 |
| 71,935 | 2026-06-12 | MoE hard fork. Blocks must carry a V2 certificate, which adds support for Mixture-of-Experts proofs. |
| 91,630 | 2026-07-23 | Dense-only soft fork. Mixture-of-Experts proofs are rejected again; only dense proofs count. |
| 96,251 | 2026-08-06 | Rank-penalty soft fork. Noise rank must be at least 128, and a higher rank makes the winning bar stricter in proportion. |
| 99,000 | 2026-08-11 | Salted noise-seed hard fork. Blocks must carry a V3 certificate: the noise seeds now also commit to the matrix sizes. |
| 120,000 | 2026-09-27 | The latest checkpoint in v1.5.2 |
What’s in this group?
- Height: how blocks are numbered, and where the number is written.
- The most-work chain: branches, reorganizations, confirmations and Pearl’s quarter-block margin.
- Forks and upgrades: the four fixed-height rule changes and the certificate versions they brought.
- Checkpoints: the twelve block hashes built into the software.
- The genesis block: block 0 byte by byte, and the Bitcoin block it quotes.
In this group
- 11.01 Height A block's place in line, counted from zero
- 11.02 The most-work chain Which branch wins when the chain splits, and by how much it must win
- 11.03 Forks and upgrades Four rule changes, each switched on at a block height fixed in advance
- 11.04 Checkpoints Twelve block hashes written into the software
- 11.05 The genesis block Block 0, its message, and the Bitcoin block it quotes