Full guide
Notes on print files
Each of these answers one question, and each is built on a number we have checked against the platform that publishes it. No general design advice.
All notes
Transparent PNG turns black on Etsy: what to uploadEtsy does not support transparency — transparent areas render as sol…Upload failed and nothing said why: what to check, in orderA print-on-demand upload that fails with no useful message is almost…Merch by Amazon dropped the 4500 × 5400 ruleFor years Merch refused any artwork that was not exactly 4500 × 5400…Why gradients and grain double your PNG file sizePNG compression scans for predictable patterns. Flat colour compress…What actually costs the most bytes in a transparent PNGAlpha is a fourth channel that compresses by the same rules as colou…What happens when Printify enhances a low-resolution filePrintify does not reject a low-resolution design. It enhances the pr…Vector vs raster: what survives a garment size runPrintful scales a design across garment sizes, so one file prints at…One master file for all four platformsBuild once at 4500 × 5400, 300 DPI, sRGB, transparent PNG. That is 1…The Redbubble 3000px rule you read somewhere is not theirsRedbubble publishes a different minimum pixel size for each product.…Printful has no published rejection line — what that means for youPrintful documents a recommended density of at least 150 DPI, and no…sRGB or CMYK: which one print-on-demand actually wantsPrint uses CMYK ink, so designers reasonably assume print files shou…