A scheme family, not a scheme.
USPS IMpb with its published Pub 199 MOD10 rail, UPS 1Z as consensus parse with a typed best-effort label, FedEx as parse-and-say-so.
Two shipping labels, blown out.
IMpb 920559012345671234567 · check 0
sum 9×3 + 2×1 + 0×3 + 5×1 + 5×3 + 9×1 + 0×3 + 1×1 + 2×3 + 3×1 + 4×3 + 5×1 + 6×3 + 7×1 + 1×3 + 2×1 + 3×3 + 4×1 + 5×3 + 6×1 + 7×3 = 170
check (10 − 170 mod 10) mod 10 = 0 → mod10 pass
1Z 12345E0205271688
check best-effort (no public UPS algorithm) — no current official UPS
document specifies the 1Z check character; the verdict says so in typesThe row.
| scheme | usps-impb · ups-1z |
|---|---|
| grammar | Per carrier. USPS IMpb: GS1-128 with AI 420 (ZIP) + the 9x IMpb structure, fully published. UPS 1Z: 1Z + shipper id + service + package id — structure by consensus parse. FedEx: format families parsed and labeled as such. |
| check digit | IMpb: USPS Pub 199 §4.6 MOD10, worked example public — mod10 pass/fail. UPS 1Z: no current official public specification of the check character — typed best-effort (no public UPS algorithm), never a fabricated pass. FedEx: parse-and-say-so. |
| canonical form | Per carrier row; identity is open, tracking status is per-caller. |
| symbologies | GS1-128 (IMpb) · Code 128 (1Z, FedEx ground) · 2D on newer labels |
| enrichment | identity: open · status: per-caller, on the caller's own carrier authorizations |
| join rule | The missing join is tracking → product identity: that repair is bridge — ranked GTIN candidates with evidence and a confidence floor, exit 1 below it. |
| pinned digest | usps-impb sha256:0abc77368c2024331748c4f2f1a403c5694e9c5f000f4eece546fd41b28ac4b5 ups-1z sha256:50376812682d08d92a8544419fc250c43e321721eb7c9a5e2f64487e85e947b4 |
| as data | /schemes/tracking.json |
In practice.
The verdict labels are the row's whole point: a pass is awarded only from a published rail, and a number whose rail is unpublished is not failed for it. If UPS publishes a 1Z specification, the row and the posts citing it revise together.
On the blog.
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Tracking numbers are a scheme family too: 1Z, IMpb, and the SSCC nobody keeps
Carrier tracking formats are proprietary grammars doing a logistic-unit identifier's job — and the parcel APIs that mint them are SKU-poor and GS1-blind. Product identity dies at the label, and the registry treats carrier formats as first-class scheme rows so the death is at least visible.
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What did I just scan? Payload identification from the first three bytes
A scanner hands you bytes, not meaning. The AIM symbology identifier, the FNC1 position, Code-39 framing, and URI shape classify any payload deterministically — worked here on ten raw payloads, the way resolve does it, from a pinned decision table rather than folklore.
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The API economy is SKU-native: the GTIN gap, measured
Across 37 verified commercial connector surfaces, GS1 identity lives only at the edges — the ERP top end, the regulated verticals, the standards rails — and is optional, unvalidated free text in the middle. Zero commercial APIs carry SSCC; two carry GLN. Product identity must be bridged into the transaction layer, never assumed.
Get an API key.
The local verbs run from npx barcoding.dev today with no key. A key opens the network half of the verb set.