Separate incompatible source groups
Group images by orientation, focal placement, and transparency before applying one crop rule.
Keep the originals immutable
Export into a new folder and include dimensions in filenames. Never make the only copy of an asset the resized version.
Verify color and transparency
JPEG replaces transparency; PNG and WebP can preserve it. Check brand marks and screenshots against both light and dark backgrounds.
Sample before committing
Inspect at least one portrait, landscape, small, and highly detailed source from the batch before using every output.
Confirm the destination contract
Write down the required width, height, accepted format, byte limit, and whether the service crops again after upload. A marketplace thumbnail, presentation background, and social card can share dimensions while applying different downstream treatment. Resize to the documented pixel box, then upload a disposable sample and inspect the result where users will see it. If the destination performs its own center crop, prepare extra safe space around the subject instead of relying on a locally perfect edge-to-edge composition.
Audit the downloaded batch
Sort the outputs by filename and confirm that every selected source has one result with the expected dimension suffix. Open files from the beginning, middle, and end of the selection order, then check unusual sources individually: very small images, transparent artwork, panorama crops, and scans with fine text. A batch can complete successfully while a single source remains unsuitable because it was enlarged too far or its important content sat outside a centered cover crop. Keep originals untouched so any exception can be corrected without generation loss.