Last updated October 2026
Help & Support
Clear answers to common barcode and Amazon FBA questions. No ticket queues. Just straight fixes you can apply right now. Or browse all free Amazon FBA label tools.
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Barcode Basics
FNSKU stands for Fulfilment Network Stock Keeping Unit. It's an Amazon-assigned code that links a specific product variation to your seller account. Find it in Seller Central: Manage Inventory → select your product → Print Item Labels. Amazon assigns the FNSKU; copy it exactly as shown in Seller Central (for example X00ABC123D).
Resellers need the FNSKU on the physical item. The EAN/UPC is used to create your Amazon listing, but for resellers the FNSKU is what goes on the label applied to the product before it reaches the fulfilment centre. Since 31 March 2026, Amazon's guidance indicates resellers use FNSKU labels on new FBA inventory. Brand Representatives may be able to use an eligible manufacturer barcode if the product meets Amazon's eligibility conditions. See our FNSKU vs UPC vs EAN guide, or check whether you need an FNSKU or UPC.
Amazon FNSKUs use the Code-128 barcode format. Our generator produces Code-128 by default when you select "Code-128 (Amazon FNSKU)" from the type dropdown. EAN-13 and UPC-A use their respective linear barcode formats. For 2D box content labels, Amazon's requirements list Data Matrix, PDF417 and QR Code; our 2D box content label generator uses PDF417.
A label with a 2D barcode (Amazon's help lists Data Matrix, PDF417 or QR Code) carrying one carton's box content information: the FBA shipment ID, each item's ID (ASIN, UPC, EAN, ISBN or FNSKU) and quantity, and expiry dates where they apply. It is one of the ways Amazon lets you provide box content information for an inbound shipment. Make them free with our 2D box content label generator.
Printing
Screen scanning isn't a reliable test — screen pixels simulate bars but don't reproduce print quality. Common print issues: scale not set to 100%, DPI too low, inkjet using colour mode instead of black-only, or glossy paper causing glare. See our full print guide.
Amazon's guidance suggests a laser printer at 300 DPI for best results. Always test-scan from the physical print before applying to stock. Using a thermal printer? Convert Amazon label PDFs with our PDF to thermal converter.
Check two things: (1) the barcode image itself — is it created at the correct physical dimensions (e.g., 2 inches wide)? (2) the label template — is the image container in your Word or Avery template set to the correct size? Sometimes the image is correct but the container is resizing it. Check the image properties in your layout software to confirm the exact dimensions in inches or millimetres. If you use the PDF from our generator, it is already drawn at the label size you chose: print it directly at 100% instead of placing it in a template.
Label Sizes
Amazon's guidance gives a label size of 1 to 2 inches tall and 2 to 3 inches wide, for example 1 × 2 in or 1 × 3 in. The 2×1 inch size fits on most products without crowding. Quiet zone: Amazon's archived item-label specification called for a quiet zone of more than 0.25 in (6.4 mm) at the left and right of the barcode and more than 0.125 in (3.2 mm) above and below it.
Our 2D box content label generator makes PDF417 labels on 4 × 6 in or 100 × 150 mm label stock, or on an A4 or US Letter page. Amazon's help says barcode labels should be printed in black on a white label at a minimum of 600 dpi. Place it on a flat face of the carton where it won't be covered or folded over an edge.
The quiet zone is the clear area surrounding a barcode. For FNSKU labels: Amazon's archived item-label specification called for a quiet zone of more than 0.25 in (6.4 mm) at the left and right of the barcode and more than 0.125 in (3.2 mm) above and below it. Keep it free of text and other print. Leave white space around the barcode on your label and test-scan a printed label before labelling stock.
Amazon Rejections
Print at 100% / Actual size (our own advice, not an Amazon rule). Amazon's guidance also points to: print resolution (a laser printer at 300 DPI for best results), covering original barcodes so they can't be accidentally scanned, and placing labels on a smooth, flat surface away from corners, edges and curves. See the shipment rejection guide for common causes and fixes.
Fees vary by marketplace and change over time. Check the current figures in Seller Central. Amazon's guidance (US) says it may refuse, return, or repackage products that arrive with inadequate or non-compliant packaging, at your expense.
Yes. Avoid shiny packing tape over the label: it can cause glare that makes the barcode harder to scan (our own advice, not an Amazon rule). Amazon's guidance calls for black ink on non-reflective paper. Never cover a barcode with tape — not even clear tape. If you need to secure a label edge, apply tape around the label, not over it.
Using the Tools
Check: (1) For EAN-13, you need exactly 13 digits. (2) For UPC-A, exactly 12 digits. (3) For Code 128 (FNSKU), paste the code exactly as Seller Central shows it. The validator message below the input field will tell you exactly what's wrong.
For printing, download the PDF. It is drawn at real label size, on the dot grid of the printer you chose in Print setup (or as a full A4/Letter sheet of labels), so print it at 100% / Actual size without resizing. PNG is the same barcode as a single-label image at your printer's resolution, for design software such as Word, Canva or Avery. Don't resize it, because that changes the bar widths. For QR codes, only PNG is available. Printing on a sheet with some labels already used? See how to print on a partially used A4 sheet.
Look at step 2 of the 2D box content label generator: every problem is listed there, naming the box and the item, and Download PDF and Print stay off until it is fixed. Common causes: the shipment ID is missing or has characters other than letters and numbers; an item row is incomplete or has a quantity of 0; the same item ID is in one box twice; or a box holds too much for one label at the chosen size and dpi (the message names a size or dpi that fits, or suggests splitting the carton). Expiry dates are chosen with a date picker, so there is no date format to type.
Privacy & Data
No data leaves your device. All barcode generation and 2D label building runs entirely in your browser using JavaScript. Your FNSKU codes, Shipment IDs, and inventory data are never sent to any server — ours or anyone else's. This is by design, not just a policy promise. You can verify this in your browser's network tab: your codes never appear in any request. When you use a tool, your browser loads the open-source libraries it needs from the public jsDelivr CDN (such as bwip-js, JsBarcode and pdf-lib). The 2D box content label generator loads three: bwip-js for the barcode, pdf-lib for the PDF and the ZXing reader that checks each label. No label data is sent in these requests.
We use Cloudflare Web Analytics, a cookieless service, to count page views and see which pages are most used. It doesn't include any data you enter into the tools. We don't use advertising cookies or sell data to third parties.
Privacy-focused by design — Barcode and label processing runs in your browser, with no product data sent to our servers. For our analytics, we use anonymised data only. See our full Privacy Policy for details.