Already rejected
Transparent PNG too large
PNG is lossless, so the content itself sets the file size — which also means there is room to optimise without touching the dimensions.
Why PNGs get this big
PNG compression scans row by row for predictable patterns. Flat colour compresses beautifully; gradients, grain and photographic texture barely compress at all. A 4500 × 5400 file of solid shapes might be 2 MB, and a photographic design at exactly the same dimensions can hit 50 MB.
Batch, auto-fix and exports
Everything above is free for one file at a time, and always will be. Doing it to a whole folder — batch checking up to 100 files, one zip with every platform file for every design, and a CSV report — is part of Seller.
Exports are padded and centred to each platform's size on a transparent canvas. Nothing is ever upscaled — a file enlarged to pass a dimension check still prints soft, which is the failure this tool exists to prevent.
Ordered by impact
- Strip metadata and re-encode — export tools embed colour profiles, thumbnails and edit history. Removing them touches no pixels.
- Bit depth and palette — if the design uses a limited palette, quantising to 8-bit PNG can cut the file to a fraction.
- Grain and texture — distressed, grainy and paper-texture effects are worst-case input for lossless compression, and usually the main source of size.
- Semi-transparent regions — edge anti-aliasing is fine, but large alpha fades collapse the compression ratio.
Frequently asked questions
Does lossy PNG compression hurt quality?
Palette quantisation is lossy and changes how gradients step. Usually invisible on flat illustration, visible as banding on photographic work.
Could I use WebP instead?
Only if the platform accepts it. Most POD upload requirements still list PNG only, so confirm before committing.