---
title: "Validate a product barcode - GTIN-8/12/13/14, UPC-A..."
method: GET
path: "/api/validate/gtin"
tags: ["validate"]
---

# Validate a product barcode - GTIN-8/12/13/14, UPC-A...

`GET /api/validate/gtin`

## Request

- Base URL: `https://2s.io`
- URL: `https://2s.io/api/validate/gtin`
- Auth: API key in header `PAYMENT-SIGNATURE`

Validate a product barcode — GTIN-8/12/13/14, UPC-A, EAN-13, or ISBN-10/13 — with the GS1 mod-10 check digit (ISBN-10 uses mod-11). Returns {valid, type, gtin14 (canonical 14-digit form, left-padded), checkDigit, reason}. Normalizes every product identifier to one GTIN-14 key so a product-master/ETL pipeline can dedupe and validate SKUs in one deterministic call instead of doing checksum math in an LLM.

## Query parameters

- `gtin` string, required
- `trial` 1

## Other responses

- `200` (unresolved $ref)
- `400`: Invalid request — not charged. error.code: BAD_REQUEST or INVALID_PARAM (parameter validation; error.details.issues lists each problem), MALFORMED_JSON, or a request-specific code. Other client errors: 405 METHOD_NOT_ALLOWED (wrong verb; see the Allow header), 413 PAYLOAD_TOO_LARGE.
- `402`: Payment required. Body is the x402 PaymentRequirements envelope with a multi-network accepts array; the per-call price is in accepts[].amount (and on the operation as x-2s-price). Sign for whichever rail you hold USDC on (EIP-3009 for Base, partial SPL transfer for Solana) and retry with the PAYMENT-SIGNATURE header (X-PAYMENT also accepted for v1 clients). Also PAYMENT_SETTLE_FAILED (error envelope) when a verified payment failed to settle: error.details.chargeStatus is "not_charged" (retry with a fresh payment) or "unknown" (the authorization may still settle before its deadline — check it before retrying).
- `429`: Too many requests — RATE_LIMITED: our per-IP / per-payer limiter. Not charged; retry after Retry-After.
- `5XX`: Server-side failure. 500 INTERNAL: unexpected error; quote error.errorId (also the X-2s-Error-Id header). 502 UPSTREAM_UNAVAILABLE (or another UPSTREAM_* code): the data provider failed — composite endpoints refuse unbilled when every source fails. 503 SERVICE_PAUSED: endpoint paused by the operator kill switch, retry after Retry-After; 503 SPEND_CAP: daily upstream budget exhausted. 504 UPSTREAM_TIMEOUT. Not charged.

---

[API](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api.md) · [All operations](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/llms.txt) · [OpenAPI document](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/revisions/da4c5caf686e?raw)