Merge CSVs

One spreadsheet.

All your CSVs, combined.

Drop CSV or TSV files here

or

No upload
Works offline
No tracking

Need to merge large datasets offline? The offline bundle handles unlimited files with no limits. $49 once.

Get Bundle →
// How it works

Three steps. Zero uploads.

01
Drop
Drop multiple CSV files. They stay on your device.
02
Configure
Choose to match headers or simply concatenate rows.
03
Merge
Download the combined CSV. Nothing was ever uploaded.
// Why this is different

Your data never leaves your machine.

Most online CSV mergers upload your files to a server. Your data passes through systems you don't control.

fwip works differently. The merge engine runs entirely in your browser. Your data is read from your device, processed on your CPU, and the result is saved back to your device. No server is involved. We literally cannot see your file.

No server processing

Everything runs on your device using WebAssembly. Your file never touches a network.

No account required

Drop a file. Get a result. No sign-up, no email, no password.

No subscription

Free in the browser. $99 once for the offline bundle. That's it. Forever.

Works offline

The desktop version works with no internet connection at all.

// Questions

Frequently asked.

What if my CSVs have different columns?▾
Use "Match headers" mode. fwip uses the first file's columns as the master and maps data from other files by column name. Missing columns get empty values.
Does column order matter?▾
In "Match headers" mode, column order doesn't matter — columns are matched by name. In "Simple concatenation" mode, columns are stacked in order.
Can I merge more than two files?▾
Yes. Drop as many CSV files as you need. They'll be merged in the order listed.
What about duplicate headers?▾
fwip uses the first file's headers. If other files have extra columns not in the first file, those columns are ignored in "Match headers" mode.
Can I reorder files before merging?▾
Yes. The file list shows all loaded files and you can remove any file before merging. Files are merged in the order shown.
// Related tools

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Rename multiple files at once.

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