A print-on-demand drop is rarely one file. It is a design applied across a dozen products, plus mockups, plus the colour variants, and each platform caps the upload at a different place: Printify at 100 MB per JPEG or PNG, Printful at 200 MB, Redbubble at 300 MB and 13,500 px. Compressing those one at a time is the kind of chore that quietly eats an evening. A batch pass fixes the boring half of the problem: drop the whole folder, set one output format and one size target, and get every file back at a predictable size with the before and after listed per file. That matters beyond convenience — when every file in a drop is the same format and roughly the same size, an upload session stops failing on one outlier and the whole set behaves the same way on the platform's own reprocessing. The part a batch tool cannot do is the per-product decision: which canvas each design needs, and whether its DPI at that print area is honest. Keep that judgement yours. Skwish processes the batch in the browser, shows each result, and hands back a single ZIP with consistently prefixed names.