Selling on more than one marketplace means the same product photo has to satisfy Shopee, Lazada, Tokopedia, Etsy, Amazon, and eBay, each with its own recommended frame and size limit. Upload the untouched phone original everywhere and every one of those listings is heavier than it needs to be; re-export carelessly for each platform and quality quietly degrades with each pass. The reliable approach is one clean master per product, resized to the frame each marketplace renders and compressed to a quality that holds detail. Skwish does both in the browser with a live before/after readout and a batch mode for the whole catalogue, so you can produce a platform-ready set in a couple of minutes, export it as a ZIP, and keep the master safe on your own machine.