Shopify's recommended size, kept small enough to not slow down store loading speed.
Target: under 1500KB
Shopify recommends product images at 2048×2048px, which is large enough for the built-in zoom feature and for most theme layouts — but at that resolution, an uncompressed photo straight from a camera or phone can easily be several megabytes, and store speed is itself a ranking and conversion factor Shopify actively measures.
A slow-loading product page directly hurts conversion rate — every extra second of load time is well documented to increase cart abandonment — so the goal isn't just matching the recommended resolution, it's reaching it at the smallest file size that still looks sharp.
They don't need to be square if your product photography isn't — Shopify displays non-square images correctly too. 2048px refers to the recommended maximum dimension, giving enough resolution for zoom without being unnecessarily large.
Well under 1-2MB per photo. A typical Shopify product page loads several images at once (gallery, related products, recommendations), so keeping each one lean has a compounding effect on page speed.
Not noticeably at 75-85% JPG quality — the drop in file size at that range comes from removing detail the eye barely registers, not from visibly softening the zoomed view.