Calamo Pro
A desktop app for the files a browser tab or Excel cannot take. Compare two exports by key, browse a file of 64 million rows, and edit it with undo. Everything runs on your computer.
Compare two exports by key
Open the old and the new file, as CSV, Excel or Parquet, also an Excel sheet against a CSV export. Calamo suggests the key column and compares at once, with the same rules as the free tool, so the same files give the same answer.
- Changed, added, removed and duplicate rows; every changed cell with the old and the new value
- F8 jumps to the next changed cell, the row details follow
- Show only the columns with changes, sort by the size of a change
- Save an Excel report with counts and a fingerprint of both files, or a copy of the new file with every change marked
Comparing two files · Reading the result · Validating a data migration
Browse a file too big for Excel
Open one file to look into it: the table is usable at once and the profile of every column follows. Codes like 00123 keep their zeros, and long numbers stay as written.
- Column profile: filled, different values, numbers, dates or text, range; the key column is marked
- Values of a column with counts, histogram, mean, median and sum
- Several filters at once, also expressions like
>10,10..20orberlin|vienna - Save the rows shown as CSV, Excel (split past 1,048,576 rows), JSON, XML or Parquet
Edit it like a spreadsheet, with undo
Change cells, rows and columns in Calamo's copy of the table; the file changes only when you save. Every change can be undone.
- Type into cells, paste blocks from Excel, drag cells and rows
- Find and replace with a preview of the cells that change, also regular expressions
- Split columns, convert dates, change case, look up columns from another file, pivot table
- Save keeps the file's delimiter, encoding, line endings and the lines above the header
Measured on big files
One desktop (AMD Ryzen 9 9900X, 59 GB RAM), version 0.1, November 2026. Your computer will be faster or slower; with less memory, Calamo works on disk and takes longer.
| File | Task | Time |
|---|---|---|
| 77 MB, 1.2 million rows | open to browse | 0.3 s |
| 4.3 GB, 64.5 million rows | open to browse | 9.0 s |
| 733 MB, 450,000 rows × 1,000 columns | open to browse | 10.4 s |
| 4.2 GB and 4.3 GB, 64 million rows each | compare by key | 53 s |
Files, privacy and the rest
- Formats: CSV, TSV and .txt in any common encoding; .xlsx, .xlsm, .xlsb, .xls and .ods; Parquet; JSON and XML
- Private: files are read from your disk and never uploaded; the app sends no file names, column names or values anywhere
- Tabs for several files, a command palette (Ctrl+Shift+P), your own shortcuts, dark theme
- Command line:
calamo old.xlsx new.csv --xlsx report.xlsxfor scripts
$49 once, no subscription
- Everything in the free browser tool
- Excel, Parquet, JSON and XML, and files of several GB
- Browse and edit one file
- Report and marked copy for sign-off
- Windows, Linux and macOS (beta); a command-line version
$49 once · for one person, up to 3 computers · 30-day refund, no questions asked. Terms
Try it free for 14 days
Download the app: everything works for 14 days, with no account and no card. Then a licence key unlocks it for good.
Questions about Pro
Can I try it before buying?
Yes. Download it: everything works for 14 days from the first start, with no account and no card. Then the app asks for a licence key.
What does “once” mean?
You pay one time for a licence for one person. There is no subscription.
What if it doesn’t work for me?
Within 30 days of buying you get a full refund, no reason needed: write to hello@calamo.io. Refund terms
Will the free tool stay free?
Yes. The browser tool needs no account and stays free. Compare two CSV files now.