Overselling happens when a sales channel keeps showing stock you no longer have — usually because a sale on another channel hasn’t synced yet — leading to cancellations, refunds and marketplace penalties. The Inventory Sync Validator detects two oversell patterns: a channel quantity that is HIGHER than the master (you are promising units you don’t have), and a zero or negative channel quantity where the master still holds sellable stock (a phantom stockout hiding real inventory). Each oversell row shows both quantities and a suggested fix — for example, lower the channel quantity to match the master, or raise it so available stock becomes sellable.

The validator joins the two files on the SKU value. By default it trims surrounding spaces and matches case-insensitively, but it still requires an exact match otherwise, because it cannot know that “TEE-001”, “TEE001” and “0TEE-001” are the same product. When the same item is written differently in each file, it appears as “missing on the channel” in one and “orphan on the channel” in the other. The fix is to standardise SKUs to one consistent format across every system — this is also the single best way to prevent real sync errors.

The tool only reads the two files you give it and reports the differences — it never changes your live inventory and never connects to a store, channel or marketplace. It produces a report and suggested fixes so YOU can apply the corrections in your own systems. Because the two snapshots can be from different moments, re-export both at the same time so they reflect the same state, and keep a backup before acting. After fixing, re-run the validator to confirm the files now agree.

The Inventory Sync Validator is 100% client-side: both CSV files are read, joined and compared on your own device with an in-browser parser, and nothing is sent to a server, logged or stored. That matters because inventory exports reveal your real stock levels, SKUs, supplier relationships and channel data — information you would not want to hand to a cloud reconciliation tool that uploads your whole stock file just to diff two columns. It even works offline once cached. Only the report you choose to export ever leaves the page.