Printing USPS shipping labels on a Mac

USPS Click-N-Ship supports 4x6 thermal labels properly. The trouble is that the choice is made before the label is generated, not at print time — so by the time you notice, the file is already the wrong shape.

Choose the format first

At the print step, Click-N-Ship offers a standard 8.5 x 11 PDF and a 4 x 6 label format. This is a content decision rather than a print setting.

• 4 x 6 — the PDF is the label and nothing else. Print at 100% on a 4x6 paper size and you are done.
• 8.5 x 11 — the label sits on part of the page with a receipt portion below it. Meant for office paper, folded and taped.

The receipt is worth knowing about, because it explains why the Letter page looks so empty around the label. A good part of that page is deliberately not label, and squeezing all of it onto a 4x6 roll shrinks the real label to a fraction of the space.

The blank-label trap

This is the USPS-specific failure and it looks alarming: the printer pulls a label through and produces nothing at all.

It is usually a raw thermal format rather than a PDF. Raw label languages are instructions written for the printer to execute, not documents to be rendered. Hand one to the normal macOS print path and the driver has nothing it recognises to draw, so you get a blank label — or a page of stray characters.

Download the PDF version and print it from Preview. If blank labels continue after that, the cause is the printer rather than the file, and the pattern tells you which fault it is — all blank, every other one blank, and one-then-several are three different problems.

Print settings

1. Download the PDF rather than printing from the browser tab.
2. Open it in Preview, File → Print, then Show Details.
3. Select the thermal printer first, so the size list populates.
4. Paper Size to 4 x 6 or 100 x 150 mm.
5. Scale at 100%, Margins none.

Browsers apply their own scaling and margins to a PDF preview, which is why the same file can print correctly from Preview and badly from a tab.

When you already have the Letter version

Common enough: the format defaulted, or someone else generated the label. The label is then a rectangle on a page and no print setting recovers it — fitting the page to the roll takes everything down to roughly half its intended size, barcode included.

Crop it with our free browser tool. It finds the label, cuts it out without rescaling, and the file never leaves your machine.

Priority Mail and flat-rate labels

Flat-rate and Priority labels carry more printed matter than a plain parcel label — service banners, barcodes and routing marks that fill the 4x6 area completely.

That leaves no slack. A label already using its full width has nothing spare to lose at the edges, so a paper size that is slightly wrong shows up here first, as a clipped edge, while smaller labels seem fine.