The upload passed and it still printed blurry

The problem lives between "warning" and "rejection"

Not one of the four publishes a DPI rejection threshold. Merch by Amazon used to come closest, refusing anything that was not exactly 4500 × 5400 — but that was a dimension rule, not a density one, and Amazon has since dropped it; its editor now takes anything above 485 × 485. The others document a recommended density and stop there: Printful says at least 150 DPI and explicitly frames low resolution as a warning to check rather than a refusal, Printify says 300, Redbubble says under 200 DPI is unlikely to satisfy customers. None of them tells you where the refusal line sits, because for practical purposes there is not one. A file below every recommendation still uploads, still lists, and still sells.

Three causes that have nothing to do with DPI

• The background is baked into the pixels — it looks white but it is opaque white, and it prints as a box on a dark garment.
• Downscaled then re-enlarged — shrunk to clear a size ceiling, then blown back up to the required dimensions. The size check passes; the information is gone.
• Large-format products — the same file is crisp on a sticker and mush on a tapestry. On Redbubble the high-margin categories are exactly the large ones.

Frequently asked questions