How to stop a supplier import from wiping your stock to zero
The classic disaster: a supplier sends a half-written or empty file, the import treats every missing product as "out of stock", and your store shows nothing available until someone notices.
Common causes
The file was cut off. A partial download or a truncated export has fewer rows than usual.
"Missing means zero" settings. Some imports set any product not in the file to 0, including products from other suppliers or ones you make yourself.
The stock column moved or became text. "In stock" / "Out of stock" can't become numbers.
The link returned an error page. A login page or expired link imported as data.
Protecting yourself without an app
Compare the row count with the last file before importing.
Never import "set missing to 0" across your whole catalogue.
Keep the last good file so you can re-import it.
How Fieldwork Supplier Feed Sync guards against it
Missing items are left alone by default. If you choose "set their stock to 0" instead, it only applies to items this feed matched on earlier runs, never your other products. It never deletes products.
Mass zero-stock hold: if more than 25% of matched items would drop to zero at once, the run is held and nothing is written. This check applies once at least 10 items match.
Cut-off file hold: if the file has more than 20% fewer rows than the last good run (adjustable), the run is held. (This needs a previous good run to compare with, so it can't fire on a feed's first run.)
Empty files, web pages instead of data, JSON, unreadable Excel files and files with an unclosed quote are rejected rather than read as zero rows.
Quantities that aren't whole numbers are reported as bad rows, and too many bad rows (over 5%) holds the run.
Fieldwork Supplier Feed Sync is coming soon to the Shopify App Store.