Merge CSV Files
AvailableCombine several CSV files into one.
Merge CSV Files
AvailableNothing to show yet
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First row is a header
With headers, columns are matched by name and extra columns are kept.
Validated locally: file type, size and browser support are checked before anything runs
Preparing your file
Reading the file locally and checking that its type and size match what this tool expects. Nothing has been uploaded.
Converting locally
CSV, TSV, JSON, and basic XLSX processing use browser-native APIs and the included ZIP reader.
- Read
- Validate
- Convert
- Package
You can leave this tab open in the background — the conversion keeps running on your device, and progress is reported when you come back.
Conversion complete
Your converted file is ready to download.
Nothing to show yet
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Nothing to show yet
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Output format
CSV
Duration
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Processed
On your device
Size change
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The converted file was assembled in your browser and is released when you leave or reset this page
Something went wrong
The conversion could not be completed. Nothing was uploaded, and no partial file was saved.
This conversion is not supported yet
Your file passed every local check, and this is exactly where the Spreadsheet engine engine takes over. It does not implement this particular input and output pair yet, so nothing was converted and no download was offered.
| Engine | Spreadsheet engine |
|---|---|
| Frontend module | static/engines/spreadsheet-engine.js |
| Extra downloads | None — this tool runs on browser APIs alone |
| Runs in a worker | No — the browser is fast enough here |
| Processing | On your device |
This page is the integration point. When the engine lands, it is loaded here and the same six states drive the real conversion.
No upload for supported tools — the file is processed by this browser
Up to 50 MB