Verify a serialized GTIN (gs1:verificationService)

curl --request GET \
  --url https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}

const options = {method: 'GET'};

fetch('https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}"

	req, _ := http.NewRequest("GET", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Get.new(url)

response = http.request(request)
puts response.read_body

{
  "gtin": "<string>",
  "serialNumber": "<string>",
  "verifiedAt": "2023-11-07T05:31:56Z",
  "scanHistory": {
    "consumerScans": 3,
    "distinctRetailLocations": 2,
    "firstSeen": "2026-04-01T10:00:00Z",
    "retailerScans": 2,
    "totalScans": 5
  },
  "anomalies": [
    {
      "type": "<string>",
      "description": "<string>",
      "priorEvent": {
        "location": "49.2827,-123.1207",
        "retailer": "RetailerA",
        "scannedAt": "2026-04-10T14:30:00Z"
      }
    }
  ]
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "error": "<string>",
  "detail": "<string>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

Verification

Verify a serialized GTIN (gs1:verificationService)

Verify a serialized GTIN scan.

Tiered response:

Unauthenticated — minimal payload (verificationStatus, gtin, serialNumber, verifiedAt, recommendation). Throttled at 60 requests / hour per IP. Unknown serials return the same shape as known-authentic to prevent enumeration.
Authenticated (X-API-Key) — full payload including scanHistory counters and anomalies array. No anonymous rate limit.

Path parameters mirror GS1 Digital Link AI ordering: 01 (GTIN) + 21 (serial). Returns 422 for malformed GTIN or serial.

Experimental (v1): This linkType response shape is published as a v1 experimental contract. The auth-tier split, response fields, and verificationStatus enum may change before the first external integration freezes the shape.

GET

resolver

api

verify

{gtin}

{serial_number}

Verify a serialized GTIN (gs1:verificationService)

curl --request GET \
  --url https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}

const options = {method: 'GET'};

fetch('https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}"

	req, _ := http.NewRequest("GET", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://www.closient.com/resolver/api/v1/verify/01/{gtin}/21/{serial_number}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Get.new(url)

response = http.request(request)
puts response.read_body

{
  "gtin": "<string>",
  "serialNumber": "<string>",
  "verifiedAt": "2023-11-07T05:31:56Z",
  "scanHistory": {
    "consumerScans": 3,
    "distinctRetailLocations": 2,
    "firstSeen": "2026-04-01T10:00:00Z",
    "retailerScans": 2,
    "totalScans": 5
  },
  "anomalies": [
    {
      "type": "<string>",
      "description": "<string>",
      "priorEvent": {
        "location": "49.2827,-123.1207",
        "retailer": "RetailerA",
        "scannedAt": "2026-04-10T14:30:00Z"
      }
    }
  ]
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

{
  "error": "<string>",
  "detail": "<string>"
}

{
  "type": "<string>",
  "title": "<string>",
  "status": 123,
  "detail": "<string>",
  "error_code": "<string>",
  "timestamp": "<string>",
  "retryable": false,
  "retry_after": 123,
  "owner_action_required": true,
  "details": "<unknown>"
}

Path Parameters

gtin

string

required

GS1 GTIN-8/12/13/14 (AI 01) of the serialized trade item. Validated as 8-14 ASCII digits; non-digit input returns 422 invalid_gtin.

serial_number

string

required

Per-trade-item serial number (AI 21). 1-20 printable ASCII characters per GS1 General Specifications; out-of-range input returns 422 invalid_serial.

Response

Authenticated response payload — minimal plus history and anomalies.

verificationStatus

enum<string>

required

Verification status. Unknown serials always return authentic (enumeration protection). The internal unverified state is never exposed -- it collapses to authentic on the public contract until Phase 3 ships positive-authentication rules.

Available options:

authentic,

suspect,

counterfeit_suspected,

serialization_error

gtin

string

required

Echoed GTIN-8/12/13/14 from the request path.

serialNumber

string

required

Echoed AI 21 serial component from the request path.

verifiedAt

string<date-time>

required

Server timestamp of when this verification response was generated.

recommendation

enum<string>

required

Action recommendation. proceed for authentic and unknown serials; flag_for_review for suspect, counterfeit_suspected, or serialization_error.

Available options:

proceed,

flag_for_review

scanHistory

ScanHistoryOut · object | null

Aggregate scan counters. null when the serial has never been observed (the enumeration-safe path returns full fields populated to zero on the unauth tier; on the auth tier we expose the truth and return null so callers can distinguish 'never seen' from 'seen-but-zero'.

Show child attributes

Example:

{
  "consumerScans": 3,
  "distinctRetailLocations": 2,
  "firstSeen": "2026-04-01T10:00:00Z",
  "retailerScans": 2,
  "totalScans": 5
}

anomalies

AnomalyOut · object[]

Anomaly rules triggered for this serial. Empty when no rule has fired. Phase 1 only emits duplicate_retail_scan.

Show child attributes

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Verify a serialized GTIN (gs1:verificationService)

Path Parameters

Response