Vehicle listings fail on upload in a very specific way, and it is almost always a number rather than a quality judgement. Boats Group — the platform behind Boat Trader, YachtWorld and boats.com — caps each photo at 15 MB and caps the whole listing at 50 MB combined, recommends 2160x1440 (3:2) and sets 1080x720 as the minimum, noting that anything under 1000 pixels reads as low quality. Bring a Trailer goes the other way on one axis: the uploader caps each file at 10 MB, and photos under 1 MB may fail to upload at all, because bidders expect roughly 2000-3000 pixels on the long side and 1-4 MB per photo. Read those two together and the safe shape for almost any vehicle listing is clear: a 3:2 crop, 2000-3000 pixels on the long side, and a file somewhere between 1 MB and 10 MB. A phone burst of 60 photos at 8 MB each is both too heavy for the 50 MB listing cap and pointless for a gallery that renders at 1200px wide. Compress to the window, not to the smallest possible file. Skwish does that in the browser with a per-file readout, a batch queue and a ZIP download — nothing is uploaded, so unlisted inventory stays on your machine.