Combine multiple CSV files into one
Combine multiple CSV files into one. Choose a vertical merge to stack rows from every file into a single longer file, or a horizontal merge to place the files' columns side by side into a single wider file. You can reorder the files before merging and preview the result before downloading.
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You have monthly export files with identical columns and need one combined CSV for the year.
Input
jan.csv, feb.csv, mar.csv (same schema)
Output
combined.csv, one header, 3 files’ rows concatenated in order
Files are stacked with the header kept once and column order reconciled by name, so a reordered column in one file does not silently misalign data. It warns on schema mismatches rather than producing a corrupt merge.
Combine multiple CSV files into one. Choose a vertical merge to stack rows from every file into a single longer file, or a horizontal merge to place the files' columns side by side into a single wider file. You can reorder the files before merging and preview the result before downloading.
Vertical merge (append rows) takes the first file as the base and appends the data rows of each following file beneath it, skipping the repeated header rows so the combined file has one header. The files are concatenated in the order you arrange them, so this is the right choice when every file shares the same column layout, such as monthly exports of the same report.
Horizontal merge (merge columns) joins the files by row position: row 1 of file A is followed by row 1 of file B, row 2 by row 2, and so on, producing rows that are the concatenation of each file's columns. The output uses the longest file's row count and pads shorter files with empty cells so columns stay aligned. This is a positional side-by-side combine, not a database-style JOIN on a key column, so it works best when the files are already in matching row order. There is a header toggle that controls whether subsequent files' header rows are kept or dropped.
Stack monthly CSV reports that share the same columns into a single annual dataset.
Reassemble files that were previously split for emailing or batch processing.
Combine files that are already in the same row order so their columns sit next to each other in one file.
No. Horizontal merge combines files by row position (row 1 with row 1, row 2 with row 2), not by matching a shared key. For key-based lookups, sort both files into matching order first.
There is no hard limit. Performance depends on total row count and your browser memory.
This tool does not deduplicate. Run the merged file through the CSV Duplicate Remover to find and drop duplicate rows.
Rows and columns are parsed and transformed in memory in your browser. No record ever reaches a server.