Merge CSV Files (Append or Join)
Combine two CSV files — stack rows (matching columns by header name) or join them on a shared key column like a VLOOKUP.
How to use
- 1Paste the first CSV on the left and the second on the right (both with headers).
- 2Choose Append to stack rows, or Join and enter the shared column name.
How it's calculated
Append: columns are matched by header name; missing columns are left blank. Join (left join): every row of the first file gets the matching columns from the second file where the key values are equal.
Frequently asked questions
What if the files have different columns?
Append creates the union of all columns and leaves blanks where a file doesn't have that column.
What happens to rows with no match in a join?
They're kept with empty values for the second file's columns (a left join), just like VLOOKUP returning blank.
Can I merge more than two files?
Yes — merge two, then paste the result on the left and the next file on the right.