What barcode does USPS use?
USPS shipping labels use the Intelligent Mail Package Barcode (IMpb), a format specific to USPS that encodes your tracking number along with routing information. It’s generated automatically the moment you buy postage, through USPS.com, Click-N-Ship, or a shipping platform like Shippo, Pirate Ship, or your marketplace’s own label tool. Not something you build from scratch.
Can you generate a USPS barcode on this site?
No, and we’d rather tell you that than ship something that looks right and doesn’t scan correctly at a USPS facility. IMpb uses different encoding logic from the formats we’ve built and verified (EAN-13, UPC-A, Code 128, Code 39). If you’re trying to print a shipping label, use USPS.com or your shipping platform directly. That’s also the only way to get a barcode tied to a trackable postage purchase.
What if you just need a tracking or reference barcode for your own use?
If you want to encode a USPS tracking number for your own internal records, not for the shipping label itself, that’s plain text and works fine in Code 128.