Merge CSV files online by column name
Combine exports under one header. Columns match by their exact names, so a different column order will not move values into the wrong fields.
Choose files or try the synthetic example.
Some cells start with characters that a spreadsheet may interpret as formulas, including minus signs. Quoting a CSV cell does not prevent formula execution. Only open files from sources you trust. Values have not been changed.
How to use this tool
- Choose two or more UTF-8 CSV files that use the same separator. The displayed file order is the append order.
- Check the separator and select Read files, then merge the files. Columns from later files join the end of the header. Missing values stay blank.
- Check the preview and row count, then download the combined CSV.
Try a small example
The synthetic example combines two exports with id and name columns in different orders. The result has three data rows under one header. IDs 001, 002 and 003 keep their leading zeros.
What to check before downloading
This appends rows. It does not join records by ID, remove duplicates, or add source filenames. Headers match exactly, including case and spaces. For repeated monthly imports or larger files, use a saved Power Query workflow or a local script.
The preview shows the first five data rows and eight columns, with cells shortened to 120 characters. Downloads contain the full result. Output uses UTF-8, commas, quoted fields and CRLF record endings. Your original files stay unchanged.
Can I combine CSVs with different headers?
Yes. The output includes every distinct header in first-seen order. A row gets an empty value for any column missing from its source file. Check for accidental differences such as Name and name before downloading.
Will Excel keep my leading zeros?
These tools preserve text such as 001 and long identifiers in the downloaded CSV. A spreadsheet can still convert them when opening it. Import identifier columns as text. A CSV cannot restore digits that were already lost.
Related tools and guides
- Remove CSV duplicates by selected columns
- Split CSV into smaller files with headers
- Combine CSV exports with different column orders
- CSV import troubleshooting guides
Sources
- RFC 4180: CSV quoting and record structure
- Microsoft: leading zeros and large numbers
- OWASP: spreadsheet formula interpretation in CSV files
Testing notes
Automated JavaScript tests cover quoted fields, embedded line breaks, Unicode, malformed records, column matching and output row counts. The tools operate on CSV text. They do not test Excel or Google Sheets import behavior.