About LabelStack

Why the project exists

LabelStack is a free web app for people who print barcodes for a living: Amazon FBA sellers, Etsy shops, warehouse ops, small presses, and anyone laying Code 128, UPC, EAN, or FNSKU onto Avery sheets. It runs entirely in your browser. There is no account, no upload API, and no server that stores your catalog.

The project exists because hosted barcode generators ask for the one file you should not hand over: a CSV of FNSKUs, GTINs, and product names. That file is a map of what you sell. LabelStack parses it with JavaScript on your machine, validates GS1 check digits on the row, draws vector SVG bars, and builds a PDF in memory. If you open the network inspector during export, your rows are not in a POST body.

How the generator works

CSV parsing uses PapaParse in the page. Symbology checks (length, charset, X-prefix for FNSKU, GS1 modulo-10 for UPC/EAN/ITF-14) run on each spreadsheet row and cite the row number. Bars are drawn as SVG rectangles, then painted into a multi-page PDF with the published Avery or A4 geometry—not a screenshot of the preview. There is no watermark and no row cap. The only ceiling is memory in this browser.

Avery 5160 is 1.000″ × 2.625″, 30-up, 0.1875″ side margins, 0.500″ top and bottom. We use those numbers, not “about an inch.” FNSKU is Code 128 with an X-prefix, not a UPC. EAN-13 4006381333931 has a check digit of 1; 4006381333932 is a bad row. Those details are the product. A generator that rounds the grid or skips the checksum is how a pack bench reprints a hundred stickers.

Editorial standards

We publish original guides on print alignment, symbology choice, FBA labels, check digits, SVG print quality, bulk CSV workflow, homemade GTINs, laser vs inkjet stock, warehouse bin labels, ISBN-13, Letter vs A4, and test-scanning. Editorial copy is written by the LabelStack editors from printing practice. It is not scraped from manufacturer PDFs, not spun from other “barcode generator” landing pages, and not a keyword doorway with three sentences.

Guides name measurements, failure modes, and what we will not do (issue GS1 prefixes, replace Amazon’s required shipment PDF, print postage). When a guide is wrong, email contact@labelstack.app with the slug and the correction. We update the page and the “updated” line. We do not publish guest posts, paid reviews of label stock, or affiliate roundups of “best UPC services.”

Independence

LabelStack is not affiliated with Amazon, Avery Dennison, Etsy, or GS1. Avery, FNSKU, and related names are used to describe compatible sheet sizes and formats. Retail GTINs must still be licensed from GS1; this site encodes digits you already own. Amazon inbound rules live in Seller Central, not here. If a policy page at Amazon disagrees with a practical note in our FBA guide, Amazon wins.

Ads, analytics, and what we never collect

Optional advertisements (Google AdSense, publisher ca-pub-9456541586301398) may appear on pages after the site is accepted into the publisher network. They never appear on the PDF and never cover the download control. The generator works if ads are blocked. Analytics (Google Analytics, measurement ID G-G9PEDMQ1BC) records page views and named tool events such as “export PDF,” not barcode values, file names, or CSV contents.

Preferences such as template and theme may sit in localStorage on this device. Inventory rows do not. There is no account because there is nothing to store. Details: privacy and terms.

Questions, corrections, or press: contact. Site: https://labelstack.app.