When to compare spreadsheets
You tweaked a dataset and need to know what changed; a vendor file should match your baseline; after merge or dedup you want proof nothing was lost. Eyeballing thousands of rows fails. ComTools Excel Compare (Tools/Excel/Compare) takes file A and file B and lists differences.
How comparison works
| Item | Details |
|---|---|
| Formats | .xlsx, .xlsm, .xltx, .xltm, .csv |
| Scope | First worksheet only |
| Headers | Row 1 → column names (JSON keys) |
| Method | Rows aligned by index; cells compared as display text |
| Output | “Identical” or up to 200 diff lines |
Both files are converted to JSON arrays server-side, then compared. Missing rows on one side are reported; column names should match for meaningful field diffs.
Steps
- Open Excel Compare.
- Pick or drop file A (left) and file B (right).
- Click Compare.
- Read results: row count mismatch, missing rows, cell value changes.
- Clear to start over.
What diffs look like
- Row count differs (e.g. A has 100 rows, B has 98)
- Row N missing in A or B
- Row N, column
Email: A =a@x.com, B =b@x.com
Common scenarios
| Scenario | Tip |
|---|---|
| Before/after export | Save A before processing, B after |
| Vendor reconciliation | Align headers first |
| After merge | Export a sheet and compare |
| Before JSON for frontend | Compare, then Excel to JSON |
Limits and tips
- First sheet only—move the target sheet to index 1 in Excel, or split and compare one file.
- Display values—dates/numbers compare as formatted text, not raw types or formulas.
- Column order—headers match by name, not position.
- >200 diffs—list truncates with a count; for full diff, export JSON and use dev tools.
- Large files—server parse takes time; wait for status.
Related workflow
Export A / B → Compare → fix → dedup → SQL
- Remove duplicates
- Excel to SQL
- Text diff — for pasted JSON/text
FAQ
Different column names?
Comparison uses the union of keys; align headers when possible.
CSV vs xlsx?
Yes, if the first table structure aligns.
Formula differences?
Compared values are formatted cell text, not formula strings.
vs Excel side-by-side?
No desktop Excel required; automatic summarized diffs for quick acceptance.