CSV Merge Tool

Merging Spreadsheets Without Opening Excel

You have a customer list in one spreadsheet and their order history in another. Both have an email or customer ID column, but the data lives in two separate files. Combining them by hand means scrolling back and forth, copying values, and hoping you do not misalign a row. A proper merge does this in one pass by matching the shared column.

This tool performs the equivalent of a SQL LEFT JOIN. Every row from your first file stays in the output. If a matching row exists in the second file based on the column you selected, those extra columns get attached. If no match exists, the new columns are simply left blank rather than dropping the row.

When You Actually Need a Merge vs a Simple Append

If File A and File B have the exact same columns and you just want all the rows together, that is an append — stack one under the other. A merge is for when the two files describe different aspects of the same entity: one file has names and emails, the other has purchase amounts, and a shared ID links them. Confusing the two often produces a result with the wrong number of columns or duplicated data.

Handling Mismatched Column Names

Real-world CSVs rarely use identical header names across systems exported by different software. One export calls it CustomerID, another calls it Cust_ID. This tool lets you select the matching column from each file independently, so the header text does not need to match exactly — only the underlying values do.