A print-on-demand printer expects a file sized to the real print area at around 300 DPI, saved as a PNG with a transparent background, in the sRGB colour profile, with nothing on the canvas you do not want printed. Get those five things right and most files pass, but miss one and the print can come out small, blurry, boxed in white or speckled.
This checklist is for sellers who make their own artwork, or who edit AI-generated or bought designs before listing them. Providers differ in the details, so the rules below are framed as what printers commonly ask, with their own numbers linked, and your provider's product template wins wherever they disagree. For the step-by-step version, see how to make a print-ready file for print on demand.
The checklist at a glance
| Requirement | What printers commonly expect | How to check |
|---|---|---|
| Pixel size | Print width and height in inches times the DPI | Read the canvas size in pixels, not the DPI tag |
| Resolution | 300 DPI for most products, lower for large format | Divide the pixel width by the print width in inches |
| Format | PNG for apparel, SVG where vector is accepted | Check the extension against the provider's list |
| Background | Transparent wherever no ink should go | View the file over a dark and a light colour |
| Colour | sRGB profile, not converted to CMYK | Check the profile in your export settings |
| Edges and stray pixels | Clean edges, no specks or half-transparent haze | Zoom to 100% over a contrasting background |
| File size | Under the provider's upload limit | Check before uploading large PNGs |
Pixel size and resolution
Resolution only means something next to a physical size. Printify recommends 300 DPI for JPEG and PNG files, and 120 to 150 DPI for large-format products (Printify file requirements). Printful asks for 150 to 300 DPI depending on the product, and adds the rule that matters most: "Make sure the file is sized to match the actual print dimensions to ensure DPI is calculated correctly" (Printful file guidelines).
So work in pixels. A design meant to print 12 inches wide at 300 DPI needs 3,600 pixels across. A file that is 1,200 pixels wide can only print 4 inches wide at 300 DPI, whatever its metadata says. Stretch it to 12 inches and it becomes an effective 100 DPI, which shows as soft edges and blur. Typing a new DPI number into an export dialog adds no detail. Only more pixels do.
Print areas vary too. Printful's standard front print area on select DTG tees is now 15 x 18 inches, which replaced the older 12 x 16 (Printful print areas). Other providers use other templates, so download the one for the exact product you are listing. Our explainer on what DPI means for print files covers the maths in more depth.
Format and transparency
For apparel, PNG is the safe default. Printful says "PNG is usually the best option because it supports transparent backgrounds", and warns that JPEG does not support transparency, so transparent areas can print as white (Printful file guidelines). A white box around a design on a black shirt is almost always a JPEG, or a PNG exported with a white background layer still switched on.
Transparency has to be real. Some downloaded "transparent" images have a grey and white checkerboard baked into the pixels. Open the file over a coloured background: if the checkerboard is still there, the background is part of the picture. Our guide to exporting a transparent PNG for a t-shirt walks through the export settings.
SVG suits vector designs such as lettering and flat shapes, and some providers accept it with its own size cap, for example 20 MB for SVG at Printify against 100 MB for JPEG and PNG (Printify file requirements). Printful's limit is 200 MB and 20,000 x 20,000 pixels (Printful file guidelines).
Do not mix up the print file and the listing photo, because they follow different rules. Etsy does not support transparent PNGs as listing photos (Etsy image guidelines). The transparent file goes to the printer, and a mockup goes to Etsy.
Colour mode and what the method can print
Screens and many print workflows run on RGB. Printful recommends creating and uploading final print files in the sRGB IEC61966-2.1 profile, and says converting to CMYK before upload can "unnecessarily reduce the available color information" in an RGB-based workflow (Printful colour profile). Unless your provider asks for CMYK, keep the file in sRGB.
What can be printed also depends on the method. DTF transfers carry a white ink layer, which lets them work on any fabric colour (Printify print methods). All-over sublimation works the other way: "The color white can't be printed on all-over print products", so white parts of the design show the base material instead (Printful print guidelines). Design with the method in mind. For more on colour, see RGB or CMYK for print on demand files.
Clean edges and no stray pixels
A printer prints what is in the file, including things you cannot see at normal zoom. The usual culprits:
Leftover specks from background removal, scattered around the design.
A faint halo of half-transparent pixels along the edges, which can show as a thin outline or a haze on dark fabric.
A forgotten layer, guide or signature near the edge of the canvas.
Soft shadows and glows that fade towards transparent and can print patchy.
To catch them, view the file at 100% over a dark colour, then over a light one, and scan the whole canvas, not just the design. Delete anything outside the artwork that should not print, and keep the artwork itself at full resolution. Our guide on removing a background cleanly for print covers the fixes.
How Alomations prepares print files
Every design in Alomations comes back print-ready at 12 inches and 300 DPI, which is 3,600 pixels on the long side, as a transparent PNG with an SVG alongside. One design gives you a light and a dark version, so it reads on white garments and on black, and tone rules per garment colour decide which version each colour gets (automatic, and you can override it). A light variant turns lettering white even where it touches the drawing, and a dark variant keeps painted art and line drawings readable.
When a file needs work, the Design Editor (on paid plans) puts the tools from this checklist in one place: background removal in one click, an eraser and crop on image layers, enlarge a photo that is short of pixels, redraw flat art as vector, outlines and fit to canvas. Our catalog apparel is printed with DTF, with sublimation for the products that need it. The full list is on features.
Frequently asked questions
Is 300 DPI always required?
No. 300 DPI is the common recommendation for apparel and small items, but providers name lower figures for large-format products, such as 120 to 150 DPI at Printify. What matters is enough pixels for the print size the product uses.
Can I upload a JPG for a t-shirt?
Some providers accept it, but a JPG has no transparency, so any background area can print as white. Use a PNG with a transparent background unless the design is meant to fill a full rectangle.
Should I convert my file to CMYK before uploading?
Only if your provider asks for it. Printful recommends sRGB and notes that converting to CMYK can throw away colour information in an RGB-based workflow.
Why does my design print with a thin outline?
Usually because of half-transparent edge pixels left by background removal or a soft brush. Clean the edge, or add a deliberate outline, and check the file over a dark background before you upload.
If you want every design to arrive as a print-ready PNG and SVG, try the free plan.