Private data workbench

Compare CSVs by key.

Find added, removed and changed values even when row order changes. Everything is processed locally in this browser.

Before / After

Before

After

Delimiter

Key columns (1–2)Use Ctrl/⌘-click for a compound key. Options appear after input.

Prefix formula candidates with apostrophes

Enter a CSV on each side.

Limits: 5 MB / 100,000 data rows / 500,000 cells per input. Values stay as text and CSVs never leave this browser.

Added keys exist only in After; removed keys exist only in Before.
Changed rows show each changed cell. Added or removed columns are compared by header name.
Duplicate keys, blank keys and malformed CSV stop the comparison safely.

Review the exported CSV before opening it in spreadsheet software. Formula-candidate safety is opt-in.