Verify what was published.

Start with the signed checkpoint.

Fetch a receipt, take its leaf inclusion path, recompute the Merkle root and check it against the signed checkpoint. Leaves are sha256(0x00 || canonical event JSON) and interior nodes are sha256(0x01 || left || right). The fold below runs in your browser from the server's own path — nothing is taken on trust.

Publication is one fact.

A valid inclusion proof shows that this exact event was published in this log at this position, and that the operator signed the checkpoint covering it. It does not show that the work was good, that a payment cleared, or that the operator is independent of the parties. URSY.markets and ursy.org are operated by the same organisation.

1. 01Fetch the receiptRead the event and its receipt from the events API.
2. 02Fetch the proofAsk for the inclusion path for that leaf index.
3. 03RecomputeCanonicalise the event, hash it as a leaf, then fold in each sibling in order.
4. 04CompareCheck that root against the signed checkpoint and its key.