How does Merge CSV work?

Stack several CSVs into one, aligning columns by header name. Add your files above, adjust anything you want to change, and press the button. The result downloads straight to your device.

Are my files uploaded anywhere?

No. This tool runs entirely in your browser. Your files are read into memory, processed on your device, and discarded when you close the tab.

Do I need an account?

No. Every tool on FileTools360 works without signing up, and there is no watermark on the output.

What is the file size limit?

100 MB per file. Since everything runs locally, your device's available memory is the real constraint.

SpreadsheetLosslessRuns in your browser

Merge CSV

Stack several CSVs into one, aligning columns by header name. The conversion is lossless — every pixel, sample or byte in the source is preserved.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

CSV and TSV · up to 100 MB each

or paste files from your clipboard

Ready when you are

Stack several CSVs into one, aligning columns by header name. Everything happens in this tab; nothing is sent anywhere.

⌘K to search converters

How to use it

1
Add your files
Merge CSV works with CSV and TSV. Drop them in, browse for them, or paste from your clipboard.
2
Put them in the right order
The files are processed top to bottom. Drag them to rearrange before you start.
3
Run it and download
Press the button and save the result. Everything happens on your device, and nothing is uploaded.

About these formats

Accepts

Comma-Separated Values

Flat tabular text — one table, no formatting.

Extensions: .csv
MIME type: text/csv
Best for: Data imports and exports · Databases · Scripts
Compatibility: Every spreadsheet, database and programming language.

Accepts

Tab-Separated Values

Like CSV but tab-delimited — safer for text with commas.

Extensions: .tsv, .tab
MIME type: text/tab-separated-values
Best for: Data pipelines · Text containing commas
Compatibility: Wide, especially in data tooling.

Columns are matched by header, so files with different column orders still line up. Missing columns are filled with blanks rather than silently shifting your data.

Good to know