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How to compare two CSV files and see which rows were added, removed or changed

Updated

Comparing last month's export with this month's is a common job: new customers, cancelled orders, changed prices. Comparing line by line only works if both files are sorted the same way; matching rows by a key is far more reliable.

Pick a key that identifies each row

A good key is stable and unique: an order number, SKU, customer ID or email address. With a key, rows can be in any order and still be matched. Without one, you can only check whether whole rows are identical.

In Excel or Google Sheets

  1. Put both files in the same workbook, on two sheets (Old and New).
  2. In the New sheet, add a column with =COUNTIF(Old!A:A, A2)=0 (A = the key column). TRUE means the row is new.
  3. Do the same in the Old sheet against New to find removed rows.
  4. For changed rows, look up each key's values in the other sheet (XLOOKUP in Excel, VLOOKUP or XLOOKUP in Google Sheets) and compare them with a formula such as =B2<>XLOOKUP(A2, Old!A:A, Old!B:B).

This works, but it gets slow and error-prone with many columns, because every column needs its own comparison.

The private way: in BenchCove

Free, no sign-up. Uses the File & Data Workbench. Nothing is uploaded.

  1. Open Compare in the File & Data Workbench and load the original and the new version (CSV or Excel). Both stay in your browser.
  2. Match rows by key columns (BenchCove suggests likely keys such as an ID or email) or by identical rows.
  3. See the counts of added, removed, changed and unchanged rows, and which columns changed most.
  4. Filter the differences, see the old value for each changed cell, and export the result as CSV.
Compare two files in your browser

Questions

Do the files need to be sorted?

Not when you match by a key column: rows are found by their key wherever they are. Only line-by-line comparisons need identical sorting.

What if a key appears twice in one file?

Then the key isn't unique and matches can be ambiguous. Remove duplicates on that key first, or combine two columns into a key.

Can I compare an Excel file with a CSV?

Yes. BenchCove reads .xlsx/.xlsm and CSV files, so the two versions don't need to be the same format.