How to use Merge CSV files
- Load the example to check the expected input shape, or select your file. Keep a separate copy of the original.
- Review the options and rules below. Run the tool, then compare representative values, row counts and headers.
- Copy the output or download a new file. Input changes clear the previous result so you cannot download stale output.
Rules and limitations
Select 2–20 files, with a combined size up to 5MB. Encoding, delimiter, header names and column order must match. Rows are appended in the displayed file order; the header appears once. This operation does not join by key or remove duplicates.
Worked example
Use the English example button above. Identifiers such as 0012 are strings; they should not silently become 12. For conversion, compare record counts before and after. For cleaning, filtering, comparison and lookup, check the operation-specific summary.
The two example files each have three data rows and matching headers. Merge produces six data rows and one header. Repeated IDs remain because merge does not deduplicate.
Troubleshooting
If columns shift, check the delimiter and quote fields containing delimiters or newlines. If characters look wrong, select the encoding before loading the original file again. CSV has no stored cell types; spreadsheet software may infer numbers and dates when opening it.
Does my file leave my device?
The tool processes selected files and pasted input in browser memory. It does not upload the file or its name. Hosting providers may process page-request metadata such as IP address and requested URL. See the privacy notice.