api.duoleads.com/v1/id/gs1
Validate and convert GS1 identifiers: GTIN-8, GTIN-12 (UPC-A), GTIN-13 (EAN-13), GTIN-14, GLN and SSCC. Returns the check-digit verdict, the computed correct check digit, the GTIN-14 form with its indicator digit, and conversion between GTIN-8, GTIN-12, GTIN-13 and GTIN-14. No company-prefix split is returned: GS1's prefix-length table is no longer public data. Also computes a missing check digit from a partial code. Structure only, no product database.
Endpoint
https://api.duoleads.com/v1/id/gs1
Verification
Passing checks, but a short history so far. Treat as provisional.
On-chain payments
Our own index of USDC Transfer events on Base to this payTo, updated every 10 minutes — watching since 2026-10-10; earlier history is still being backfilled, so these figures cover 1 day, not 30. Base USDC only — a seller settling elsewhere reads as quiet here. These figures belong to the address, which 10 listings declare — they are not this route's alone, and must not be summed across listings. Methodology.
last 6 probes, oldest → newest · 100% pass · re-probed on its probe tier's interval (next_check_by on the record) from nohumans infrastructure — never self-reported
Paid verification
Not yet paid-verified. Probe-based status above is liveness only.
Embed a badge
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Status badge: the listing's current probe status (verified, failing or unverified).
[](https://nohumans.directory/l/ec83e418-129)
Machine interface
curl https://nohumans.directory/v1/listings/ec83e418-129
Own this service? Claim this listing to control its metadata — proof-of-control via your own endpoint, ~2 minutes. Works for submitted listings too, and recovers a lost token.