Bitcoin Metaprotocols Ordinals

Ordinal Theory

Casey Rodarmor's scheme (2022) for numbering individual satoshis. Each of Bitcoin's ~2.1 quadrillion sats has a unique number based on mining order, allowing them to be tracked through transactions.

Numbering scheme

Sats numbered 0, 1, 2, ... based on:

• Mining order (block + position).
• First-in-first-out (FIFO) through inputs/outputs.

When a tx has inputs [A1, A2] and outputs [B1, B2]:

• Sats from A1 flow to B1 first, then overflow to B2.
• Within A1, sats are ordered by their original numbers.

Sat rarity classes

Casey defined a fan-following hierarchy:

• Common: any sat.
• Uncommon: first sat of each block.
• Rare: first sat of each difficulty epoch (every 2016 blocks).
• Epic: first sat of each halving (every 210k blocks).
• Legendary: first sat of each cycle (every 6 halvings, ~24 years).
• Mythic: sat #0 (the first sat ever; in Satoshi's coinbase).

Some collectors pay premium for rare sats.

ord client

Reference implementation:

• github.com/ordinals/ord (Rust).
• Indexes the entire chain to compute sat ordinals.
• Provides:
  • Wallet for sending specific sats (avoid spending rare ones).
  • Inscription creation/viewing.
  • REST API for querying.

Heavy index: full ord index ~1+ TB on a recent chain.

Indexed services

• ordinals.com — primary explorer.
• mempool.space integration for ordinal viewing.
• OrdiScan, Ordinalsbot — third-party services.

Use cases

• Sat collecting — buying / selling rare sats.
• Foundation for inscriptions, BRC-20, Runes, etc.
• Provenance tracking — proving a sat originated from a specific block.

Compared to UTXO

Ordinals are an interpretation layer; Bitcoin consensus has no notion of ordinal numbering. The ord client computes ordinals by parsing the chain. Different ord clients must agree on the numbering scheme.

Common confusions

• "Ordinals" = sat numbering. Inscriptions = data attached to sats. They're different concepts often conflated.
• ord client requires txindex + ord-specific indexing.
• "Mythic sat" is just one specific sat (sat #0); not a category of thousands.

See also

• inscriptions/SKILL.md
• brc-20/SKILL.md
• runes/SKILL.md
• atomicals/SKILL.md