Prepend a CSV Column

Prepend a CSV Column adds a new column at the beginning of your CSV. You can insert row numbers, UUIDs, or a custom value. Modify CSV structure instantly right in your browser.

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Supported file types: .txt, .csv, .tsv, .log, .json, .xml, .md, .ini, .yaml, .yml, .html, .htm, .css
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How to Use:

  • Paste CSV data into the “Input Text” box or click “Choose File” to upload a local file
  • Supported file types: .txt, .csv, .tsv, .log, .json, .xml, .md, .ini, .yaml, .yml, .html, .htm, .css
  • Enter a column name in the “Column header” input defaults to ID if left blank
  • Use the “Value mode” dropdown to control what data goes in the new column:
    • Row Index adds the line number (starting at 1)
    • Random UUID inserts a unique identifier per row
    • Custom Value repeats a specified string (e.g., “Label”) for each row
  • If “Custom Value” is selected, enter your string in the visible field next to it
  • Output updates live in the right-hand box and flashes blue each time it changes
  • Below the output, a character counter shows the live total length of the generated CSV
  • Click “Prepend Column” to manually trigger re-processing
  • Click “Copy Output” to copy the new CSV to your clipboard
  • Click “Export to File” to save your updated CSV as a .csv file
  • Click “Clear All” to reset all input, output, fields, and selected file

What Prepend a CSV Column can do:

Prepend a CSV Column gives you a quick way to add extra identifiers or structure to your data. Add row numbers for indexing, UUIDs for uniqueness, or custom tags to categorize rows. The tool works instantly and completely offline, making it a solid utility for prepping files for spreadsheets, databases, or bulk imports.

Example:

Before:

name,age,email
Alice,30,[email protected]
Bob,25,[email protected]

After (Row Index mode):

ID,name,age,email
1,Alice,30,[email protected]
2,Bob,25,[email protected]

Common Use Cases:

Prepend a CSV Column is great when you need to add tracking IDs, row counters, or type labels to existing CSVs. Whether you’re preparing bulk data for import, labeling datasets, or just adding structure before transforming your file, this tool lets you do it quickly without extra scripts.

Useful Tools & Suggestions:

If you’re preparing data to prepend, Create a Random CSV is a quick way to generate matching rows. And after prepending, Rename CSV Columns helps make sure everything’s still labeled correctly.

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