The slowest part of running a store is not design but resizing dozens of images to each platform's spec. The wrong dimensions get squashed, the wrong ratio crops the subject, and a non-compliant white background can hurt search ranking.
1. Platform specs (2026)
- Taobao / Tmall main image: 800x800 or larger, 1000x1000 recommended, square, white background preferred, under 3 MB.
- JD main image: 800x800, also with a margin so the subject is not cropped at the edge.
- Pinduoduo main image: 750x750, square.
- Detail page: fixed 750 px wide, any height, under 500 KB per image.
- Main image video cover: 1:1, 800x800 recommended.
2. Batching the resize properly
Dropping dozens of images in and exporting 800x800 needs two settings:
- Fit mode "crop to fill": guarantees a square output with no white bars; if the subject touches the edge, crop in with a margin first.
- Keep the aspect ratio: stretching a non-square original distorts it, so use "fit inside" or "crop to fill", never stretch.
The entry point is e-commerce batch resize: pick the spec, process everything at once in the browser, and skip the server queue.
3. Why main images get rejected
- The subject occupies too little of the frame (aim for 70% or more);
- Watermarks, stitching or borders;
- A background that is not white (mandatory in some categories);
- Blurry images -- usually a slice cut from a long detail-page image and then enlarged.
4. Balancing compression and sharpness
Around 200 KB balances clarity and load speed. If the image contains promotional text, export PNG or JPG at quality 90 to avoid colour artefacts around the letters.