When two exports should describe the same real-world rows, the reliable approach is to pick one or more columns that uniquely identify each row together — a composite key. Examples: invoice number, customer id + billing period, or SKU + warehouse code.
Why key columns matter
Without a stable key, row order differences look like data changes. With a key, Columnics aligns rows across File A and File B so you can trust “only in A”, “only in B”, and “changed values” views.
Steps in Columnics
- Upload both files (or one workbook with two sheets). Parsing stays in your browser.
- Select the sheet on each side, then choose the columns that form your row key.
- Optional: adjust case sensitivity, spaces, or partial matching if your keys don’t line up exactly.
- Press Compare now and review results; export slices to Excel when you are ready.
Columnics runs locally in the browser — useful when spreadsheets must not be uploaded to a third-party server.