Merge CSV Files
Combine multiple CSV files into a single table
Runs 100% in your browser — nothing is ever uploaded.
What is Merge CSV?
Paste two or more CSV blocks (separated by ----- lines) and get one combined CSV: with the header option on, the first header row is kept and duplicate headers from the other files are dropped automatically. Perfect for joining monthly exports, log chunks or split datasets back together.
How to use Merge CSV
- Paste your CSVs into the input box or click “Load sample” to try it.
- Adjust the options in the toolbar if needed (root name, format, delimiter …).
- Click the convert button — the CSV output appears instantly in the output pane.
- Copy the result with one click or download it as a file.
ConvertLab FAQ
Is the CSV merger free?
Yes — 100% free, no signup, no limits, no watermarks. Use it as often as you like.
What happens to the header rows of each file?
When “first row is header” is enabled, the header of the first block is kept and the first row of every following block is skipped, so the merged file has exactly one header. Disable the option to concatenate all rows as-is.
Is my data uploaded to a server?
No. Everything runs entirely in your browser with JavaScript — your data never leaves your device, which makes the tool safe even for confidential files.
Are these converters free?
Yes — every ConvertLab tool is 100% free with no signup, no limits and no ad walls.
Is my data uploaded anywhere?
No. All conversions (JSON, CSV, XML, YAML, INI, .env) run entirely in your browser. Nothing ever leaves your device.
Do these tools work offline?
Yes — once the page is loaded, every converter works without an internet connection.