Merge two CSV files

Combine two CSV files by appending rows, unioning columns, or joining on a key.

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ToolCSV Merge
Input
Output
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Preview

How it works

The inputs are parsed, then append, union, or key-based join determines the row and column shape. Optional whole-row deduplication runs after the merge and the result is serialized with the chosen delimiter.

  • Append is the least-surprising default for matching columns.
  • Union and join are explicit because they change shape or identity.

Worked example

Append two user lists
Concatenate two CSV files with the same columns into one combined file
Input
											Input1: id,name,email
1,Alice,alice@example.com
2,Bob,bob@example.com
Input2: id,name,email
3,Carol,carol@example.com
4,Dave,dave@example.com
Output
												id,name,email
1,Alice,alice@example.com
2,Bob,bob@example.com
3,Carol,carol@example.com
4,Dave,dave@example.com

When to use this

Monthly exports append, unlike schemas union, and catalogue data joins inventory on SKU.

Edge cases

  • A repeated join key in the second input keeps its last lookup row.
  • Union fills absent columns with empty values rather than shifting cells.
  • Deduplication compares the complete merged row, not only the join key.

References