GS1 Digital Link QR

GS1 Digital Link is a URL syntax that encodes product identifiers (GTIN, lot, serial, expiry) as path segments after a base hostname - so a single QR code is both a human-friendly link and a machine-parseable product identifier. Retail buyers (especially DACH grocery), EU pharma post-FMD, and supply-chain auditors increasingly require GS1-conformant QR codes on packaging instead of standalone 1D barcodes.

Reference: GS1 Digital Link spec .

URL syntax

The encoded URL has the form:


https://<host>/01/<gtin>[/10/<lot>][/17/<expiry>][/21/<serial>]

AI	Meaning	Format
`01`	GTIN (mandatory)	8, 12, 13, or 14 digits
`10`	Batch / lot	up to 20 alphanumeric chars
`17`	Expiry date	YYMMDD
`21`	Serial number	up to 20 alphanumeric chars

The order in the URL is AI numeric order (01 → 10 → 17 → 21), not the order you fill the form. Most parsers tolerate any order, but emitting in numeric order keeps you portable.

Endpoint


POST /v1/qr/gs1

Body:


{
  "host": "b.elido.me",
  "gtin": "09520123456788",
  "application_identifiers": {
    "lot": "ABC1",
    "serial": "SN001",
    "expiry": "270101"
  },
  "format": "png",
  "error_correction": "Q",
  "size": 1024
}

Response:


{
  "url": "https://b.elido.me/01/09520123456788/10/ABC1/17/270101/21/SN001",
  "png": "<base64 bytes>"
}

The endpoint returns:

200 - { url, png|svg }. Use format: "svg" for vector printing.
400 - missing host or gtin, unparseable JSON, unknown format.
422 - GTIN check digit mismatch, invalid AI value (lot too long, expiry not YYMMDD, etc).

Worked example 1 - milk carton

A litre of organic milk with a printed lot code, no serial, no expiry on the QR (the human-readable best-before date stays on the label):


curl -X POST https://qr.elido.app/v1/qr/gs1 \
  -H "Authorization: Bearer $ELIDO_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "host": "b.elido.me",
    "gtin": "09520123456788",
    "application_identifiers": { "lot": "L260509A" },
    "format": "svg",
    "error_correction": "Q"
  }' \
  --output milk.json

The QR encodes:


https://b.elido.me/01/09520123456788/10/L260509A

A buyer scanning this with a phone gets a landing page (your dashboard chooses what to render); a warehouse imager parses the path and extracts GTIN 09520123456788 + lot L260509A for stock rotation.

Worked example 2 - OTC pharmaceutical (FMD-aligned)

EU Falsified Medicines Directive requires GTIN + serial + expiry + lot on every commercial pack. The QR carries all four:


curl -X POST https://qr.elido.app/v1/qr/gs1 \
  -H "Authorization: Bearer $ELIDO_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "host": "b.elido.me",
    "gtin": "04006381333931",
    "application_identifiers": {
      "lot": "B22A41",
      "serial": "PFX9000123",
      "expiry": "281231"
    },
    "format": "svg",
    "error_correction": "H"
  }' \
  --output pharma.json

The QR encodes:


https://b.elido.me/01/04006381333931/10/B22A41/17/281231/21/PFX9000123

Use error_correction: "H" for pharma. Pharma cartons see harsh handling; H-level (≈30% recovery) tolerates scuffs that would kill a Q-level code.

Validating GTINs

The endpoint validates the GS1 mod-10 check digit before generating. Invalid GTINs come back as 422 with a stable error message:


{ "error": "invalid GTIN: check digit mismatch (expected 8, got 7)" }

The check digit is the right-most digit; it’s computed by alternately weighting the other digits by 3 and 1 (right-to-left, starting with 3) and taking (10 - sum mod 10) mod 10. The dashboard’s GTIN field runs the same check live as you type - paste the 13-digit body of your EAN and the field shows you the expected check digit.

Quiet zone & error correction

The renderer emits a 4-module quiet zone on every side, matching the GS1 General Specs §5.5.2.5 minimum. You don’t need a separate “GS1 mode” flag - the default rendering pipeline is conformant.

For error correction:

Q (≈25% recovery, our default) - fine for retail packaging on glossy stock.
H (≈30% recovery) - required for pharma, recommended for uncoated cardboard or anywhere a printer might smudge.
L and M - not recommended for packaging; only for digital display or paper handouts.

Tier gate

GS1 QR is a Business+ feature on the dashboard. The endpoint returns 402 Payment Required for lower tiers; the UI greys the form and shows an upgrade CTA.