How it works
Validate that both parsed header rows match exactly, then append all data rows from the second table to the first.
Input definitions
- First CSV
- Plain text; maximum 200,000 characters.
- Second CSV
- Plain text; maximum 200,000 characters.
A worked example
- First CSV
- name,score Ada,10
- Second CSV
- name,score Lin,20
Assumptions & limits
Plain text on your device, with no remote fetch. CSV input is comma-separated with unique nonempty headers, at most 1,000 rows and 50 columns; downloads escape spreadsheet formula prefixes.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Does merging CSV files remove duplicates?
No. Merging appends data rows and preserves duplicates. Use the separate duplicate-row remover after merging if exact duplicates should be removed.
How does Merge CSV tables with matching headers work?
Validate that both parsed header rows match exactly, then append all data rows from the second table to the first.
What are the limits of Merge CSV tables with matching headers?
Plain text on your device, with no remote fetch. CSV input is comma-separated with unique nonempty headers, at most 1,000 rows and 50 columns; downloads escape spreadsheet formula prefixes.
How do I keep the full worksheet?
Run the tool and choose Download file. The on-page table is a preview and may show only the first 20 rows; the downloaded file contains the full result. CSV downloads escape spreadsheet formula prefixes. Inputs and files are processed on your device.