Combine CSV files into one

How files are combined

• Order: rows are added from the top file in the list down. Use “Up” and “Down” to change the order.
• Matching columns: columns whose header names are exactly the same are matched automatically. Extra spaces or different upper/lower case count as different names. If one file has several columns with the same name, they are matched in the order they appear.
• Columns with other names: under “Column matching”, choose which column each one goes into, or add it as a new column.
• Column order: follows the first file with a header row. Columns that appear for the first time in later files are added after it.
• Files without a header row: untick “First row is a header” to match columns by position (column 1, column 2, …).
• Missing values: columns a file doesn’t have are left blank. Rows with fewer values are filled with blanks too.
• Too many values: if a file has a row with more values than its header, nothing is combined, so no values are lost. The file name and row number are shown; check the delimiter and “First row is a header”.
• Empty lines: lines with nothing in them are skipped.

How values are handled

Values are only rearranged as text. Nothing is converted to numbers or dates, and spaces are not trimmed. Leading zeros (00123), long numbers, date-like values and line breaks inside quotes are all kept.

In the saved CSV, only values containing the delimiter, a quote or a line break are wrapped in quotes (“). A value that had unnecessary quotes in the original file is saved without them; the value itself is the same.

Values starting with =, +, -, @ and similar may be treated as formulas by spreadsheet apps. The tool tells you how many there are but does not change them.

When Excel opens the file, it may still show leading zeros or long numbers as numbers. That depends on how Excel imports the file.

Encoding

Files are read as UTF-8. If a file can’t be read, you can choose another encoding for it (Shift_JIS (CP932), EUC-JP, UTF-16, Windows-1252). The encoding is not detected automatically. The result is saved as UTF-8, with or without a BOM.

Excel files (.xlsx) can’t be read. In Excel, save them as “CSV UTF-8 (Comma delimited)” first.

Limits

Up to 20 files, 30 MB each and 60 MB in total. The combined table can have up to 1,000,000 data rows and 1,000 columns.