When this tool helps
Use this immediately before a BASE CSV + image ZIP upload. It compares image references in the CSV with files in the ZIP and separates missing images, duplicate basenames, and malformed CSV structure before you reach the upload screen.
With hundreds of images, manual filename comparison is not a realistic quality-control method. Let the checker produce the differences, then review only the exceptions.
The CSV needs an image column before matching can happen
If the CSV contains no image-related column, there is nothing meaningful to compare against the ZIP. The checker now treats that as a template-level problem instead of reporting a clean result. CSV quoting and structural errors are also surfaced before image matching.
BASE requires the image filenames in the CSV to match the files packaged for upload. Similar-looking filenames are not enough.
ZIP matching uses the basename
For CSV-to-ZIP comparison, the checker uses the final filename component. If the same basename appears in multiple ZIP folders, the reference becomes ambiguous and is flagged. Non-ASCII image filenames are also called out because they can conflict with documented BASE guidance.
The ZIP size is checked against the upload limit as well. If you need to split a large upload, keep each CSV and its image ZIP as a matching pair.
A practical example
A CSV references `item001.jpg`, but the ZIP contains only `item01.jpg`. Or the ZIP contains both `images/item001.jpg` and `old/item001.jpg`. These are exactly the small differences that are hard to spot by eye and easy to catch before upload.
Finish with a small real upload and verify that images land on the intended products in the intended order.