Withdata DataFileConverter merges CSV files into one Excel file locally — any number of files, mapped column by column, with the output options of your choice. 100% local, secure, and cross-platform.

Why Choose Withdata DataFileConverter as a CSV Merger?

🔒 100% Local & Secure

All merging runs on your own computer. Nothing is uploaded to any cloud server.

⚡ Fast Streaming Merge

Millions of rows within a minute. Large files are streamed with low memory usage.

📁 Any Number of Files

Add two files or a whole folder, then combine everything into a single Excel file.

🔄 Column Mapping

Files with a different column order or extra columns can be mapped to the output columns before merging.

🖥 Windows, macOS, Linux

Native builds for Windows, macOS and Linux, with a step-by-step GUI wizard and a command line interface.

⏱ CLI & Scheduled Tasks

Save a merge session and run it automatically from Windows Task Scheduler or crontab.

Full Feature Comparison

Feature	Supported details
Input	Any number of CSV files, added one by one or as a folder
Output format	Excel
Merge mode	All input rows into one output file
Running mode	GUI wizard · command line · scheduled tasks
Column handling	Source columns are mapped to the output columns
Output options	Column mapping, encoding, header row
Platform	Windows, macOS, Linux (native, 64-bit)

CSV to Excel — What Changes

Each CSV line becomes one worksheet row and the header row becomes the first row of the sheet. Anything past 1,048,576 rows is split across sheets, and columns that look numeric are stored as numbers rather than text.

All CSV Merge Options You Need

Merge several CSV files into one Excel file — step by step in the GUI wizard
Merge a whole folder of CSV files in one run
Map the columns of each input file to the output columns
Run the merge from the command line, and schedule it as a scheduled task
All CSV tools and all Excel tools
Guide: Merge multiple CSV files into one Excel

Same source format, other targets

This page merges CSV into another format. If you need a different output, these pages each do that one job:

All merge tools, by format

Merging into Excel — Notes

The delimiter and quote character can be chosen; quoted fields and embedded line breaks are parsed correctly.

How to Merge CSV Files (4 Steps)

Open Withdata DataFileConverter and choose Merge (combine multiple files into one).
Add the CSV files you want to merge — two files, a list, or a whole folder.
Check the preview and map the source columns to the output columns; then set the output options (Column mapping, encoding, header row).
Click Convert — the single Excel file is written in seconds. Save the session if you want to run it again from the command line.