Barcodes

A modern US comic carries a 12-digit UPC-A and, to its right, a small 5-digit add-on. The UPC names the series (and the publisher, through its first six digits); the add-on, by the direct-market convention, names the issue:

• ISBN (an EAN-13 starting 978 or 979): collected editions and graphic novels. A 5-digit add-on on a book is usually its price: a currency digit (5 is US dollars) then the price, so 51999 is $19.99.
• ISSN (an EAN-13 starting 977): magazines, with the issue in a 2-digit add-on.
• EAN-13 with a 5-digit add-on: comics from outside the US sometimes print these.

Known UPC prefixes tell the publisher and whether a copy is a newsstand or direct-market edition:

Look up a barcode takes the main code and, separately, the add-on. It answers how it read the code (the symbology, whether the check digit is right, and what the add-on suggests) and the candidate editions, best first. Each candidate has a score (0 to 1) and the reasons behind it, strongest first. The exact edition comes first when the catalog knows the code; then what the series and the add-on suggest.

curl 'https://collection.id/api/v1/catalog/barcode?code=759606089369&addon=00311'

import { createCollectorClient } from '@collector/sdk';

const collector = createCollectorClient();

// The 12 digits under the bars, and the 5 small digits to their right.
const { barcode, candidates } = await collector.lookupBarcode({
  query: { code: '759606089369', addon: '00311' },
});

if (barcode.comic) {
  // A hint, not an identity: publishers don't always follow the convention.
  const { issueNumber, coverVariant, printing } = barcode.comic;
  console.log(`The add-on suggests issue ${issueNumber}, cover ${coverVariant}, printing ${printing}`);
}

for (const candidate of candidates) {
  console.log(
    `${candidate.seriesTitle} #${candidate.number}`,
    candidate.editionName ?? '',
    `score ${candidate.score.toFixed(2)}:`,
    candidate.reasons.join('; '),
  );
}

• Digits that aren’t a UPC, EAN or ISBN are 400 invalid_barcode; a wrong check digit is 422 checksum_failed (usually a misread digit).
• Signed out, lookups are limited to 60 a minute per network. Signed in, candidates also include Metron’s.
• To combine a barcode with what the cover says and a photo of it, a signed-in collector can use Identify a book from evidence.