Long to Wide Format Converter
Choose identifier, key, and value columns to reshape CSV locally. Duplicate identifier and key pairs are reported instead of overwritten.
Choose identifier columns. In wide-to-long mode, every other column becomes a key/value row.
A QUICK WALKTHROUGH
How to use this tool
- Paste CSV with a header row.
- Choose long-to-wide or wide-to-long and select the relevant columns.
- Review the result or duplicate report, then copy or download the CSV.
Both directions
Long-to-wide uses one or more identifier columns plus a key and value column. Wide-to-long keeps selected identifier columns and turns each other column into a key/value record.
Duplicate combinations are reported
If an identifier combination and key would occupy the same output cell more than once, conversion stops and lists the conflicting source rows. No value is silently discarded.
CSV stays in your browser
Parsing and reshaping run locally. Quoted commas, line breaks, and escaped double quotes are supported; input is limited to 2 MB, 50,000 records, and 500 columns.
GOOD TO KNOW
Common questions
What is a duplicate key combination?
It is more than one row with the same identifier values and key value. Those rows compete for one output cell, so this tool reports them and does not create a pivot.
Can I convert wide data back to long?
Yes. Select the identifier columns to keep; the remaining columns become key and value rows.
Is my CSV uploaded?
No. The data is processed in your browser.