Merge CSV Files Online

Instructions

1. Paste each table with its header and select the delimiter for each input.
2. Union includes every header and fills missing fields with blanks.
3. Strict requires the same set of header names, even when their order differs.
4. Review the merged preview and download.

Understanding your result

Union mode combines the sample headers ID, Name and Team. Ada receives a blank Team because that field is absent from the first table. Strict mode rejects that difference. Choose the mode based on whether missing columns are acceptable in your destination.

What to do if you have a problem

If header matching fails, check spelling, capitalization and spaces in both tables. If rows have the wrong width, inspect quoted commas and the delimiter setting for each input. Use a join tool when your aim is to match records by ID rather than append rows.

What to know before using the result

Header matching is exact and case-sensitive. Headers must be unique and nonempty, and every row must match its table’s header width. Duplicate data rows are retained; this is an append operation, not a database join. Maximum 2 MB per input and 20,000 combined rows including the header.

These tools work with pasted text or supported CSV files rather than Excel workbook files. CSV exports contain values and do not preserve workbook formatting, formulas or multiple worksheets. Formula builders produce formula text to use in Excel. Data processing runs in the browser tool.

Try an example

First table: ID,Name
1,Ada

Second table: Name,ID,Team
Sam,2,Sales

Summary

Download one appended table with columns aligned by their header names.