Merge CSV files

Combining exports into one file

Many systems export one file per month, per region, per store or per report run. Monthly sales, daily logs, a CRM export per team, a form tool that produces one CSV per campaign. Analysis almost always needs them combined. Doing it by hand in a spreadsheet means opening each one, copying everything except the header, and pasting it at the bottom of the last, which is slow and easy to get wrong. This tool does it in one step.

How merging works

Drop the files in the order you want them combined. The header row of the first file is kept; header rows in the remaining files are dropped so they do not appear as data rows in the middle of the result. Every other row is appended in order. The output is a single CSV named as you choose, ready to open or import.

Headers that do not match

Merging assumes the files share the same columns in the same order, which is true for repeated exports from the same system. If the columns differ, the tool still combines the rows but the result will have misaligned data, so check that the headers match before merging files from different sources. A quick way to tell: open each file and compare the first line. If one export added a column halfway through the year, use the extract columns tool to bring them to the same set of columns first.

Order and provenance

Rows keep the order of the files and the order within each file. If you need to know which file each row came from after merging, add a column with the file name in each export before merging, or keep the files' date ranges distinct so the date column tells you.

Delimiters and encoding

Files are parsed with the delimiter detected from their content, so a comma-separated file and a semicolon-separated file can be merged. The output uses a comma. All files are read as UTF-8; if one of them is in an old Windows encoding and shows garbled accents, fix it with the encoding tool first.

Common uses

• Twelve monthly bank or sales exports into one annual file for the accountant.
• Several regional contact lists into a single mailing list, followed by the remove duplicates tool.
• Log files from several days into one for searching.
• Rejoining the parts made by the split CSV tool.

Everything runs in your browser, so financial and customer exports are never uploaded.