Compare two CSV files, and see exactly what changed.

Why a text diff is not enough

A line-by-line diff reports every line as changed when the rows are in a different order, when a column was added in the middle, or when the separator changed from comma to semicolon. The data may be identical; the diff is useless.

Comparing tables

1. Open the newer file and press ⌃⌘D (Compare with Another File). Choose the older file — or compare with whatever table is on the clipboard.
2. Choose how rows line up: by position, or by a key column such as customer_no, so re-sorted files still match. Columns line up by name, so moved columns do too.
3. Read the differences: changed values are marked character by character — 300.00 → 350.00 highlights only the digit that moved. Rows only in one file are listed.
4. Take changes across one value at a time, or a whole row at once.

Case, spacing and whole columns can be left out of the comparison, so a column of timestamps that always differs does not hide the change you are looking for.

What changed since you saved

Two versions are often the one in the window and the one on disk. File ▸ Compare with the Saved File holds the table you are editing against the file as it is saved — what you changed here, or what another program changed there — with every row and value ready to take across. And View ▸ Mark What Changed Since Saving puts a wash behind each value you edited, so the changes are visible in the grid itself before you save.

From the command line

icsv --diff yesterday.csv today.csv

opens the first file and compares it with the second, ready to read.