Image & Data
Merge CSV Files
Combine several CSV files into one, matching columns by header name and filling gaps automatically.
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Transparent methodology
What the result includes—and what it does not
Built for anyone combining exports from several periods, shops or systems into one table.
Calculation method
- 1All files are read and their headers matched by name: the output contains the union of every column, in first-seen order.
- 2Rows keep their file order; cells for columns a file did not have are left blank instead of shifting data.
Assumptions and limits
- Headers must be spelled identically to merge into the same column ('email' and 'Email' are different columns).
- File contents are processed locally and never uploaded; the only telemetry is an aggregate operation counter with no file names, column names or contents.
Worked example
Merging two marketplace exports
Input: January.csv (id, name) and February.csv (id, city).
Output: One file with id, name, city — 100% of the rows, blanks where a month lacked the column.
How to use it
Three steps. One clear answer.
- 1Enter or paste the values requested by the tool.
- 2Review the input units and choose any relevant options.
- 3Calculate, then copy or download the result you need.
Built for trust
Useful without the friction.
- No registration or paywall before your result.
- Responsive controls for phone, tablet, and desktop.
- Clear assumptions and warnings where estimates have limits.
Frequently asked questions
How does the Merge CSV Files work?
All files are read and their headers matched by name: the output contains the union of every column, in first-seen order. Rows keep their file order; cells for columns a file did not have are left blank instead of shifting data.
What should I check before using the result?
Headers must be spelled identically to merge into the same column ('email' and 'Email' are different columns). File contents are processed locally and never uploaded; the only telemetry is an aggregate operation counter with no file names, column names or contents.
How current is this page?
The methodology and source notes were reviewed on 2026-07-25. Editable rates and inputs should still be checked against the provider or authority linked below.
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