Verify GS1 product barcodes (GTIN-8
Verify GS1 product barcodes (GTIN-8, UPC-A / GTIN-12, EAN-13 / GTIN-13, GTIN-14, UPC-E, ISBN-10, ISBN-13). Validates GS1 Modulo 10 check digits, expands UPC-E, decodes country prefixes, and converts ISBN-10 to ISBN-13
Request
- x-api-key: <your-api-key>
- Content-Type: application/json
Response
{
"barcodeDetails": {
"countryCode": "PL",
"gs1Prefix": "<gs1 prefix>",
"isBooklandIsbn": true,
"isbn13Equivalent": "<isbn13 equivalent>",
"normalizedDigits": "PL61109010140000071219812874",
"originOrType": "standard",
"rawInput": "PL61109010140000071219812874",
"upcAExpandedEquivalent": "<upc aexpanded equivalent>"
},
"isValid": true,
"status": "success",
"tokensDeducted": 1,
"validationResult": {
"actualCheckDigit": "<actual check digit>",
"detectedFormat": "GTIN-8",
"expectedCheckDigit": "<expected check digit>",
"isCheckDigitValid": true,
"isFormatValid": true,
"reason": "checksum ok"
}
}What it does
Verify GS1 product barcodes (GTIN-8, UPC-A / GTIN-12, EAN-13 / GTIN-13, GTIN-14, UPC-E, ISBN-10, ISBN-13). Validates GS1 Modulo 10 check digits, expands UPC-E, decodes country prefixes, and converts ISBN-10 to ISBN-13
Request
Body
| Field | Type | Required | Description |
|---|---|---|---|
barcode | string | yes | The barcode number string to verify (e.g., "011122233344", "5900000000000", "9780321125217", or "0321125215") |
Example request
{
"barcode": "<barcode>"
}Response
| Field | Type | Description |
|---|---|---|
barcodeDetails | object | |
↳ countryCode | string | |
↳ gs1Prefix | string | |
↳ isBooklandIsbn | boolean | |
↳ isbn13Equivalent | string | |
↳ normalizedDigits | string | |
↳ originOrType | string | |
↳ rawInput | string | |
↳ upcAExpandedEquivalent | string | |
isValid | boolean | |
status | string | |
tokensDeducted | integer | |
validationResult | object | |
↳ actualCheckDigit | string | |
↳ detectedFormat | enum | One of: GTIN-8, UPC-A (GTIN-12), EAN-13 (GTIN-13), GTIN-14, UPC-E, ISBN-10, ISBN-13, INVALID. |
↳ expectedCheckDigit | string | |
↳ isCheckDigitValid | boolean | |
↳ isFormatValid | boolean | |
↳ reason | string |
Example response
{
"barcodeDetails": {
"countryCode": "PL",
"gs1Prefix": "<gs1 prefix>",
"isBooklandIsbn": true,
"isbn13Equivalent": "<isbn13 equivalent>",
"normalizedDigits": "PL61109010140000071219812874",
"originOrType": "standard",
"rawInput": "PL61109010140000071219812874",
"upcAExpandedEquivalent": "<upc aexpanded equivalent>"
},
"isValid": true,
"status": "success",
"tokensDeducted": 1,
"validationResult": {
"actualCheckDigit": "<actual check digit>",
"detectedFormat": "GTIN-8",
"expectedCheckDigit": "<expected check digit>",
"isCheckDigitValid": true,
"isFormatValid": true,
"reason": "checksum ok"
}
}Errors
Every error answers with the same envelope: an HTTP status, a machine code and a sentence.
400 | The body or a parameter failed validation. The details array names the field. |
401 | No key, a revoked key or a wrong header. Send x-api-key. |
402 | The wallet cannot cover this call. Top up or wait for the monthly grant. |
404 | The resource does not exist, or it is not yours. Both answer identically and cost nothing. |
429 | Over the per-minute quota of your tier. Back off and retry. |
5xx | Upstream refused or timed out. The call is not billed. |
Code
curl -X POST 'https://app.castomapi.com/v1/verify/barcode' \
-H 'x-api-key: <your-api-key>' \
-H 'Content-Type: application/json' \
-d '{"barcode": "<barcode>"}'const res = await fetch('https://app.castomapi.com/v1/verify/barcode', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"barcode": "<barcode>"})
});
const data = await res.json();
console.log(data);import { request } from 'node:https';
// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/verify/barcode', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"barcode": "<barcode>"})
});
const data = await res.json();
console.log(data);import requests
res = requests.post(
'https://app.castomapi.com/v1/verify/barcode',
headers={'x-api-key': '<your-api-key>'},
json={"barcode": "<barcode>"},
timeout=30,
)
print(res.json())<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/barcode');
curl_setopt_array($ch, [
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
CURLOPT_POSTFIELDS => json_encode(['barcode' => '<barcode>']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);Cost and limits
This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.
Rate limits per minute
| No key | 10 |
| Free | 60 |
| Pro | 300 |
| Enterprise | 1200 |
Questions
What does Verify GS1 product barcodes (GTIN-8 cost?
This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.
How do I authenticate?
Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.
Can I send an Authorization: Bearer token instead?
Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.
What are the limits?
10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.
OpenAPI: https://app.castomapi.com/docs/json