How these guides are checked
Every specification in these guides is traced back to what Amazon publishes, and the guides are explicit about a distinction Amazon makes and most summaries drop: the difference between what Amazon requires and what it prefers. Images must be 500 to 10,000 pixels on the longest side. Amazon separately prefers 1,000 pixels or more for zoom. An image from 500 to 999px can upload and go live, but does not zoom. Check its dimensions separately.
Each guide includes an Amazon source list. We distinguish published requirements from our own measurements and recommendations.
Limitations worth knowing
Amazon changes these rules without announcement, and enforcement differs by category and marketplace. A guide reflects what Amazon published at its last-updated date, shown on every post. The checker applies the rules that can be measured from an image file alone; it cannot see category-specific policies attached to your listing, and it is not affiliated with or endorsed by Amazon.
Commercial interest
ComplianceKit sells a paid tier. These guides recommend it, and the person writing them owns it — stated here rather than left for you to work out. The specifications are the same whether you use the tool or check by hand, and every guide gives you the numbers to do it yourself.