How Ordinals actually works

Things this project had to get right to build an inscriber, each checked against transactions on Bitcoin rather than against a specification. Written down because they were hard to find stated correctly anywhere else.

• How parent and child inscriptions work

  Giving an inscription a parent means spending the parent's own output. That one requirement turns provenance into an ownership proof that needs no login, no signature challenge and no database.

• Where an inscription goes when you spend its UTXO

  Satoshis are assigned to outputs first in, first out. An inscription follows the satoshi it sits on, which means its destination is decided by arithmetic, not by which output you meant it to land in.

• Why some inscriptions cannot be moved safely

  About one inscription in thirty-five sits somewhere that makes spending it hazardous — not because anything is wrong with it, but because of where it happens to sit in its output. Measured across 140 randomly sampled cats.

• What is actually inside an inscription

  An inscription is data hidden inside a Taproot script that never executes, revealed when the script is spent. Here are the exact bytes, checked against a 105,900-byte witness item on Bitcoin.

• Commit and reveal, and what to do when a reveal sticks

  Inscribing is always two transactions, ten minutes apart, and the second one holds your inscription while it waits. Here is why, and what makes the difference between a reveal you can rescue and one you cannot.

• How to verify an Ordinals collection yourself

  There is no registry that makes a collection real. What exists is provenance on chain and lists published by marketplaces, and only one of those is something you can check without trusting anybody.

• What your wallet does with a PSBT, and how to sign safely

  Signing a transaction that spends an inscription is not like approving a payment. The defaults in some wallet APIs will sign more than you meant, and the difference is measurable.

• Inscription number, inscription id, collection index

  One inscription usually has three different numbers attached to it, and people lose track of which cat they own because of it. Here is what each one is and which to use when.

• Recursive inscriptions, with a complete worked example

  An inscription can load another inscription's content by id. C.A.T. uses it to fit 2,222 pieces of generative art into 622 KB — each cat is 114 bytes that reference a shared engine and 138 on-chain trait images.