This repository contains the working draft of a Bitcoin Improvement Proposal (BIP) tentatively titled “Non-monetary UTXO Cleanup (The Cat)”.
It documents a soft-fork consensus change and new spending rules intended to remove an existing, snapshot-based set of non-monetary UTXOs (NMUs) created by protocols such as Ordinals and Stamps, by making those UTXOs permanently unspendable and eligible for removal from the UTXO set.
The BIP itself does not define any new relay or standardness policies for future transactions. Rather than restricting new transactions directly, The Cat aims to remove demand for such activity by eliminating the financial incentives for creating NMUs in the first place.
For motivation, tradeoffs, and the discussion of censorship resistance, see the Rationale section of the draft, in particular Censorship resistance and scope.
bip-the-cat.md- main BIP draft (specification, rationale, references)- Additional notes, scripts, and data may be added over time.
This repository serves as the public discussion link referenced in the BIP header
and in any future pull request to the bitcoin/bips repository.
- Rationale
- Censorship resistance and scope
- External indexers, determinism, and reproducibility
- Centralization and trust model for NMU generation
- Backward compatibility
The FAQ in the draft also answers common questions directly:
-
Do I need to run Ord or Stamps on my node?
See Do node operators need to run Ord or Stamps? -
What exactly do the reference indexers consider an NMU?
See What rules do the reference indexers actually use to decide which UTXOs are NMUs? -
Will spammers just find workarounds and keep spamming anyway?
See Won't spammers just make workarounds and spam anyway? -
Can users "escape" The Cat by spending dust after the snapshot?
See Can’t users just spend their NMUs after the snapshot, removing them from the list? -
Will my "inscribed sats" in normal wallet UTXOs get Catted?
See What if some of my UTXOs contain “inscribed sats”? Won’t those get “Catted”?
See charts/ for supporting statistics and visualizations that
illustrate the scale and structure of inscription-related UTXOs.
A BIP is typically circulated on the Bitcoin Development Mailing List for feedback before requesting a BIP number.
Correction (Jan 2026): In an earlier version of this README I implied that a specific reply of mine was being held back by mailing-list moderation. That was incorrect: I later confirmed I had accidentally sent that reply directly to Greg Maxwell instead of to the mailing list, so it was never submitted to the list for approval in the first place. This was my mistake, and I apologize for the confusion.
Some earlier attempts to post the draft itself were held in moderation before appearing publicly; discussion is now taking place on-list. Regardless of venue, this repository remains the canonical home for the draft specification and ongoing edits to The Cat. Feedback is welcome via issues and pull requests, and I’m participating on Bitcoin-dev and Delving Bitcoin.