The eBay Minimum Photo size (500×500px)
eBay will not accept a primary listing photo unless the longest side is at least 500 pixels, so 500x500 is the exact floor that gets a rejected image through the uploader. This size exists for edge cases: an old photo, a screenshot, or a source file that simply is not large enough to reach the recommended 1600px. Resizing to 500x500 keeps the square ratio eBay expects while meeting the bare minimum requirement.
It is important to be honest about the trade-off. At 500px eBay accepts the photo but does not enable its zoom and enlarge tools, which only switch on at 1600px, and buyers cannot inspect fine detail. On a competitive marketplace that can cost you clicks, because a small, soft thumbnail signals a low-effort listing next to sellers with crisp, zoomable galleries. Use 500x500 only when you genuinely have no higher-resolution source available.
If you do have a larger original, always prefer 1600x1600 instead; upscaling a tiny image to fake resolution just produces blur that looks worse than an honest small photo. The square 1:1 ratio still matters here so eBay's gallery does not crop your item awkwardly. Everything here resizes 100% in your browser with no upload and for free, so even a quick fix stays private. eBay's minimum and its photo policies change periodically, so verify the current threshold before you rely on the smallest allowed size.