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CSV & data / FREE ONLINE TOOL

CSV Column Mapper

Two systems can describe the same product with different headers and column orders. Build an explicit output schema and preview it before exporting. The tool changes structure; it does not infer marketplace rules.

YOUR WORKBENCH

From file to clarity.

● Runs locally

CSV only · 10 MiB per file maximum · 100,000 rows · 100 columns · 1 million cells. For mobile, start below 2 MiB.

No encoding guesswork. If characters look wrong, choose the source encoding and reselect the files.

Choose a file to see its columns.

Your file stays on this device. Import a CSV or try sample data.

⌁ No sign-up. No uploads. No analytics or advertising scripts. How local processing works

How to use CSV Column Mapper

  1. Import a CSV. Each source column starts as its own output field.
  2. Rename output fields, move them up or down, remove fields, or add a merged field with one or more ordered source columns.
  3. Choose a separator for merged values. Preview the output and download when the headers and rows match your destination.

A mapping is an ordered recipe

Output field order follows the mapping list, not the source file. For merged fields, the order of source selections is the concatenation order. The separator is inserted between every value, including empty values: “Mina”, empty and “Chen” with a space becomes “Mina Chen”. The tool does not trim values, skip blanks or transform dates.

Headers must remain unambiguous

Empty and duplicate output names are rejected after trimming. Source CSVs with empty or repeated headers are also rejected at import, because selecting one ambiguous header could silently use the wrong data. Repair the source header row in a trusted editor before importing. Missing source references stop mapping rather than produce blank columns.

Safe structure, safe downloads

Renaming or merging text can create a spreadsheet formula trigger. Exports therefore apply the same neutralization rules to both headers and values. A leading apostrophe may appear when reimporting the result as raw text. Keep an original backup and validate destination header names, required fields, encoding and value formats before any production import.

CSV format and safe export

Use comma-delimited files with a unique, non-empty header row. Quoted commas, escaped quotes, quoted line breaks, CRLF and UTF-8 BOM are supported. Whitespace-only rows are skipped. Choose the correct encoding before import; non-UTF-8 content is not guessed. Parsing and processing run in a browser Worker. Only the first 50 result rows appear in the preview; downloads contain the complete result. Outputs are also limited to 100,000 rows, 100 columns, 1 million cells and 32 MiB; expanded comparisons or merges may hit a conservative size limit earlier. Reduce fields or split files if an output limit is reached.

Exports include a UTF-8 BOM and CRLF line endings. Cells starting with =, +, − (ASCII hyphen), or @ after whitespace/control characters, and cells starting with a tab or line break, receive a leading apostrophe. Headers are protected too. Negative numbers may therefore export as text. This changes potentially dangerous cell content; the result reports the number of protected cells. Keep an untouched original.