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CSV Row Number Adder
Append or prepend exact signed integer row numbers without changing data order.
UTF-8 CSV or TSV, Pasted delimited text
Numbered CSV, JSON numbering summary
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
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How to use this tool
- Paste CSV or choose a UTF-8 file and choose Input delimiter.
- Set a unique New column name, Placement, Start and nonzero Step. Choose Protect spreadsheet formulas.
- Select Add row numbers and download numbered.csv plus row-number-report.json.
Examples
Start -2 and step 1 assign -2, -1 and 0 to three data records in their original order.
Limitations
- 5 MiB input, 50,000 data records, 500 output columns, 500,000 output cells including header and 20 MiB combined output; 30-second processing limit.
- Start and step require whole signed decimal tokens without whitespace, at most 100 digits excluding sign. Generated values have a 128-digit cap and use canonical decimal spelling.
- No numeric padding, prefixes/suffixes, ranking, sorting or group resets. The existing CSV formula policy preserves complete signed numeric tokens; CSV still cannot declare spreadsheet cell types.
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