Compare two CSV exports by key. See exactly what changed.
Drop last month's export and this month's. Calamo matches rows by ID, not by position, and shows which rows were added, removed or changed, down to the column. It runs in your browser, so your files never leave your computer.
- Matches by key column
- Column order doesn't matter
- Nothing is uploaded
- Free, no sign-up
Free CSV compare
Pick two CSV files with a header row. Comma, semicolon, tab and pipe delimiters are detected automatically.
The free tool works best up to a few hundred MB per file, depending on your browser's memory. For bigger files, Excel and Parquet, use Calamo Pro.
Why not just use Excel, a diff tool or a chatbot?
Most compare tools look at cells by position. Real exports get re-sorted, gain columns and grow past a million rows. And a chatbot needs your customer data uploaded and a very precise prompt to get it right.
Matches rows by ID
Re-sorted file? New column in the middle? Calamo pairs rows by your key, so only real changes show up.
Your data stays yours
Customer lists, payroll and price lists are not something to upload to a website or an AI chat. Calamo processes everything locally.
Built for big exports
Text-diff tools and spreadsheets choke on millions of rows. Calamo streams the files instead of loading them into a grid.
Catches the usual traps
IDs keep their leading zeros, 12.5 equals 12.50, extra spaces are not a change, and duplicate keys are flagged. Same answer every month, no prompt engineering.
What people use it for
Migration checks
Old system vs new system after an ERP or CRM migration: which records went missing, which fields were mangled.
Monthly export changes
What changed in the customer, product or employee list since last month, ready for an audit trail.
Price list updates
A supplier sends a new price list: see every changed price and every discontinued SKU.
Data pipeline QA
Compare the output of the old and new version of a job before you switch over.
Calamo Pro
In development – early access
A desktop app and command-line tool for files the browser can't handle. One payment, yours forever.
Founding-member lifetime licence. Price goes up at launch.
- Tens of millions of rows, on your own machine
- CSV, Excel (XLSX) and Parquet, and two database tables
- Fuzzy matching and de-duplication of names, companies and addresses
- Saved comparisons and a command-line tool for scheduled checks
- Windows, macOS and Linux
- Full refund if it doesn't ship or doesn't work for you
Get early access
Tell us your email and we'll send you the beta first. No spam, one email when it's ready.
FAQ
Are my files uploaded anywhere?
No. The free tool reads the files with JavaScript inside your browser tab. You can disconnect from the internet after the page loads and it still works.
What is a key column?
The column that identifies a row, such as a customer ID, SKU, email or invoice number. If no single column is unique, pick two or more and Calamo combines them.
Does column order matter?
No. Columns are matched by name. Columns that exist in only one file are listed and skipped.
How big can the files be?
In the browser, typically up to a few hundred MB per file, depending on your computer's memory. Calamo Pro is built for files of any size.
Can it compare Excel files?
The free tool reads CSV. Save your sheet as CSV, or wait for Calamo Pro, which reads XLSX directly. For other options, see how to compare two Excel sheets.
Who makes Calamo?
An independent data engineer from Europe who got tired of comparing exports by hand. Questions: hello@calamo.io