I spent 12 years on the Amazon inbound dock. Every box, every case, every unit — scanned. Over those years, I saw every barcode failure mode that exists. Here is what actually matters.
The Quiet Zone Is Non-Negotiable
Every barcode format requires empty white space on both sides. EAN-13 needs 11x the narrowest bar width. ITF-14 adds a thick bearer bar because corrugated cardboard causes ink bleed. I watched thousands of shipments get rejected because the label designer cropped the barcode right to the edge.
Which Format for Which Job
Code 128 — warehouse bins, shipping labels. Alphanumeric, high-density.
EAN-13 — retail products globally. 13 digits, GS1 prefix required.
UPC-A — retail products US/Canada only. 12 digits.
ITF-14 — shipping cartons, FBA case packs. Thick bearer bar for cardboard.
ISBN — books only. EAN-13 with 978/979 prefix.
Free Tool
After leaving Amazon I built genbarcode.org — six barcode formats, Canvas API, everything client-side. The Code 128 and ITF-14 generators are what I use most.