From Bitcoin and IPFS, in your browser. No server, no indexer trusted — this page recomputes everything below on its own.
?asset_id=…&txid=… to check any fixed-supply asset.
What this proves: (1) the asset id is SHA-256(etch txid ‖ vout) — it can only be this one etch; (2) the etch’s mint authority is zero — no new TAC can ever be valid; (3) the published opening verifies the on-chain Pedersen commitment to exactly 21,000,000. The Bitcoin tx comes from a public explorer but isn’t trusted: the asset id is recomputed locally and the IPFS blob is checked against its own content hash (the CID).
A fixed supply at genesis is one property. A separate one is that every transfer since then actually conserves value — that a spend can’t create TAC out of nothing as it moves. Tacit’s indexer checks this by walking a Bitcoin output’s ancestry backward, hop by hop, through the protocol’s transfer opcodes, re-verifying each hop’s Pedersen-commitment conservation and kernel signature until it reaches this same etch.
That code is worker/src/tac-ancestry.js — open-source, runs against the same public Bitcoin data this page uses, and takes no shortcuts through an index. Point it at any TAC-carrying outpoint yourself; it needs only a txid and vout to start walking.