What this tool does
Merge CSV Files
Each input is parsed as CSV instead of being split on raw line breaks, so valid multiline fields remain intact. Files can be aligned by a union of header names, common headers only or physical column position.
Private, local-first data tools
Merge CSV Files
Combine multiple CSV files locally, align columns by header or position, and review mismatches before downloading one complete file.
Processed in your browserNo account requiredEncoding and delimiter controlsIncomplete exports are blocked
Rows0
Columns0
EncodingAuto
DelimiterAuto
Issue groups0
Open a data file to start
The parser runs off the main thread. Once loaded, you can search, sort, validate, repair and export without an account.
How to use it
- Choose or drop at least two CSV files together.
- Select union, intersection or positional alignment and optionally add a source filename column.
- Review the merged table and download one CSV.
Common tasks
- Combine CSV files for use in Excel and match different column orders by header name.
- Combine files with different columns using a union or keep common columns only.
- Add the source filename to every merged row without uploading the input files.
Privacy and local processing
Local files are read by a dedicated browser worker and are not uploaded to an application server. File contents and filenames are not included in analytics events. Loading a public URL is an explicit direct request from your browser and may fail when the remote server blocks CORS.
Supported edge cases
- Header order may differ between files when name-based alignment is selected.
- Columns missing from one file become empty under union alignment.
- Multiline quoted values remain a single record because each input is parsed before merging.
Frequently asked questions
Do I need Excel for merging CSV files?
No. The files are merged locally in your browser, and you can open the completed CSV in Excel afterward.
Do all CSV files need identical columns?
No. Union alignment keeps every header and fills missing values, while intersection keeps only headers shared by every file.
Can I identify which file a row came from?
Yes. Enable the source filename column before merging.
Does merging upload the files?
No. All files are read and combined in the same browser worker.