Why barcodes should be SVG: quiet zone, DPI, and scanners

Modules, not pictures

Code 128, UPC, and EAN are built from a narrow module width, often called the X-dimension. Every bar is an integer multiple of that module. SVG (and the PDF LabelStack exports) draws those as rectangles. At 200% or 50% print size the ratios stay exact. A PNG is a grid of pixels: enlarge it and you get blur; shrink it and two modules can collapse into one.

LabelStack generates SVG in the browser and paints the same rectangles into jsPDF. That is why the download is scannable at 5160’s 1″ height and still scannable if you switch to 5163. The ZIP of SVGs is the un-rasterized form for tools that accept vector. The PNG ZIP is a high-resolution raster for software that will not. Never photograph a monitor and call it a barcode asset.

Quiet zone is part of the symbol

The quiet zone is the mandatory white pad before the first bar and after the last. For EAN/UPC it is typically 7–11 modules; for Code 128 at least 10. If a product name, a logo, or the die-cut crowds that pad, the scanner never locks. LabelStack insets the bars inside each label cell so the name sits above the code and the SKU below, with a gap—do not then drag a second graphic on top in another app.

Dark packaging and poly bags need more quiet zone, not less. If a 5160 FNSKU is failing on black mailers, move to a larger preset rather than inverting colors. White bars on black are a different print process and are easy to get wrong on an office laser. A “quiet zone” that is actually a dark bag showing through a clear label is not a quiet zone.

“Print at 300 dpi” is not a substitute for vector

300 dpi is a common raster target: a 2.625″-wide 5160 label is about 788 pixels wide. If you must rasterize, that is a reasonable floor. It is still worse than rectangles in a PDF, because the printer’s own RIP will resample your bitmap. Office lasers already screen halftones; a barcode should be 100% black on 100% white, not a dithered gray.

Use genuine black toner or ink, not a composite of CMYK that looks black. On inkjets, let the sheet dry before stacking. On lasers, avoid the ultra-cheap compatible toner that lays a dusty grey. Test-scan with the phone app you actually use on the floor, then with the hardware scanner if you have one. Phones are more tolerant than many warehouse guns. Passing a phone scan and failing a gun is a real failure mode; the test-scan guide covers how to catch it on a one-page proof.

Laminates, gloss, and why “more protection” can kill a scan

A glossy pouch over a barcode reflects the scanner’s own illumination. The gun sees a hotspot instead of modules. If a label must survive a warehouse, use a matte laminate made for barcodes, or a thermal transfer ribbon on actual label stock—not an office laminator over 5160 paper. For Amazon inbound, do not laminate at all.

Inkjet on glossy clone stock can also bleed: the black wicks into the white modules and the effective X-dimension grows. If bars look “fat” under a loupe, that sheet is done. Switch to laser 5160 or a pigment inkjet the wrapper actually rates for barcodes.

What to export from LabelStack

For Avery sheets: PDF, 100% scale, Letter or A4 as the preset says. For a single code to drop into a packaging die: SVG. For a marketplace that only accepts images: PNG from the ZIP, not a phone photo of the screen. If a partner asks for “high resolution barcode JPEG,” send PNG or SVG and explain that JPEG ringing around bar edges is a scan defect. The file they want is not a photograph.