The Print File Checklist: 6 Checks Before You Upload

Almost every rejected upload, blurry print and refund request I have had traces back to one of six things, and all six take under a minute to check. This is the list I run on every design before it goes anywhere near a product. Print it out if you like; the whole point is that it is boring and repeatable.

1. Pixel size

Not DPI. Pixels. DPI only means something once you fix a print size, so read the pixel dimensions first.

Placement	Size	300 DPI target
Standard front	12 x 16 in	3,600 x 4,800 px
Full front	15 x 18 in	4,500 x 5,400 px
Left chest	4 x 4 in	1,200 x 1,200 px

Build everything at 4,000 pixels or more on the long edge and you stop thinking about this per product. Full targets for mugs, stickers and posters are in the design size guide.

2. Actual sharpness at 100 percent

Zoom to 100 percent and look at the edges and any text. Your zoomed-out view flatters everything. If it is soft here, it prints soft, and the causes are covered in why your design printed blurry.

3. Transparent background, with clean edges

For DTG apparel, the background must be genuinely transparent, not white. Two failure modes:

A white box that prints as a rectangle on the garment.
A halo: a faint fringe of leftover background pixels around the artwork, usually from a rushed cutout.

Check by dropping the PNG onto a dark layer. Anything that should be invisible shows up immediately. The methods are in transparent backgrounds for t-shirt designs.

4. Color space

Export sRGB. Suppliers run RGB through their own color engines, and uploading CMYK is a reliable way to get colors you did not choose. This is also why a print never matches your screen exactly: your monitor emits light, ink does not.

If a color matters (a brand red, a specific navy), order a sample before you list. No amount of file checking substitutes for seeing ink on fabric.

5. File format

PNG for anything with transparency. This is the default for apparel.
JPG only for full-bleed products with no transparency, and even then PNG is safer, because JPG compression damages exactly the sharp edges designs are made of.
SVG where the supplier accepts vector, which is rare in POD but excellent when available. The trade-offs are in PNG vs SVG for print on demand.

6. The thumbnail test

Shrink the design to the size of a marketplace search result. Can you still tell what it is? Can you still read it?

This is the only check on this list that is about sales rather than production, and it is the one that predicts results best. Buyers meet your design at thumbnail size in a grid of forty competitors. A design that needs a full-screen view to work has already lost.

The order matters

Run them in this order, because each one is cheaper than the next to fix:

Pixels, because too small means going back to the source.
Sharpness, same reason.
Background, a two-minute fix.
Color space, a one-click export setting.
Format, same.
Thumbnail, because if it fails this the design is wrong, not the file.

Most people run this backwards: they perfect a file, upload it, and only then discover the design does not read at thumbnail size.

Where files usually go wrong

If your designs come from AI, the two recurring failures are resolution (models often output 1,024 or 2,048 pixels, which is under spec for a full front print) and near-transparent edges that leave a halo. Both are fixable, and both are why I build LzyPOD to output large transparent PNGs by default: the checklist mostly answers itself when the file starts right.

Common questions

What resolution do print-on-demand suppliers require? 150 DPI at print size is usually the accepted minimum, 300 is the target. In pixels, 4,500 x 5,400 covers a full front print.

Do I need to check every file if they all come from the same tool? Check the first few. Once you know a tool’s output size and background behaviour, you are really only checking the thumbnail test each time.

Does the supplier tell me if a file is bad? They warn about low resolution. They do not warn about white backgrounds, wrong color space, or a design that is unreadable at thumbnail size.