An illustration with sample files; your own files show their own results.
Before3 designs that would print badly
Blurry, too few pixels
White box around it
Outside the safe zone
AfterThe same designs, print-ready
Sharp at 300 DPI
Transparent PNG, no box
Inside the safe zone
Merch by Amazon Design Checker: 4500 × 5400 px Pre-Flight
A Merch by Amazon upload is a transparent PNG on a fixed canvas, 4500 × 5400 pixels at 300 DPI in this preset. A design that is the wrong size, carries an opaque background or sits too close to the edge is a rework you would otherwise find out about after uploading.
Drop your design into the tool above. The checker measures it against the preset, checks transparency and safe margins, flags colours that print badly, and exports a print-ready PNG with 300 DPI written into the file. Platforms revise their specifications from time to time, so confirm the current numbers with Amazon, or use the Custom canvas option to set your own.
POD Design Checker: DPI, Bleed and Size Check for Print-on-Demand
A print pre-flight tool for print-on-demand designers. Drop in up to 50 designs and it checks each one against a platform's real specs (Merch by Amazon, Printify, Printful, posters, mugs, phone cases, KDP covers) for resolution, safe margins, bleed, transparency and CMYK gamut, then exports print-ready files. Every pixel stays on your machine.
What it measures
Resolution is read from your file's real pixel size divided by the product's physical print size, giving the effective DPI along the limiting axis: the number the printer sees. Safe-margin checks trace your artwork's actual content and test whether it clears the safe zone. Transparency scans the alpha channel for a solid background and for the soft-edge “halo” that dirties a cut-out.
Runs in your browser
Decoding, alpha scanning, background removal, DPI compositing and DPI stamping run locally, with the heavy pixel work in a Web Worker so the batch stays responsive. Your artwork is never uploaded, which matters when designs are your inventory. Exports are built and zipped in the browser too.
Frequently asked questions
What size should a Merch by Amazon design be?
The preset checks for a 4500 × 5400 pixel canvas at 300 DPI, saved as a PNG with a transparent background. That matches the standard t-shirt specification as this preset was written, but platforms revise their requirements, so confirm the current figures with Amazon before you upload.
Why does a shirt design need a transparent background?
A garment printer prints only the artwork, so an opaque rectangle behind it would print as a solid block on the fabric. This preset expects transparency, and the check reports whether your file carries it.
Does it convert my design to CMYK?
No, and it says so rather than pretending otherwise. It flags colours, very saturated RGB values in particular, that will shift noticeably when a printer converts them, so you can adjust them first. A true conversion needs the printer's own ICC profile, which only they can supply.
Is my design uploaded anywhere to be checked?
No. The whole check runs in your browser and the file is never uploaded. Previewing and checking need no account; an account is needed only to spend tokens when you download the result.
