Merge CSV Files Online

Merge multiple CSV files into one XLSX worksheet. Learn how headers, UTF-8 text, delimiters, duplicate rows, leading zeros, and different columns are handled.

How to use this tool

  1. Select at least two CSV files.
  2. Confirm the first row contains headers.
  3. Choose source columns and identical-row removal.
  4. Merge and download the XLSX result.
  5. Verify delimiters, accents, dates, and leading zeros.

Merge recurring CSV exports into one Excel worksheet. The cleanest result comes from UTF-8 files that use standard commas and consistent header names.

Matching headers

Values are appended under columns with the same header name.

Different columns

New header names create additional output columns and blank cells where a source lacks that field.

Source tracking

Optional source columns identify the original file for every output row.

Before and after example

Before

After

Troubleshooting

Everything is in one column

Re-export the source using standard comma-separated UTF-8 format.

Accents are broken

Convert the source encoding to UTF-8.

Columns are duplicated

Standardize equivalent header names before merging.

Leading zeros disappear

Review identifier columns and treat them as text.

Frequently asked questions

Can CSV files have different columns?

Yes. Different headers create additional output columns.

Does CSV preserve Excel formatting?

No. CSV contains plain table text.

What is downloaded?

One XLSX workbook with a merged worksheet.

Can it read semicolon-separated files?

Parser behavior varies; comma-separated UTF-8 is most reliable.

Can identical rows be removed?

Yes, when all output values are identical.

Are files uploaded?

No. Spreadsheet contents are processed in the browser tab.

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