Prepend CSV Columns

What It Does

Add new columns to the beginning of your CSV data. Each new column appears before all existing columns, pushing the original data to the right. Useful for adding identifiers, row numbers, or category labels at the front of a dataset.

How It Works

Prepend CSV Columns produces new output from rules, parameters, or patterns instead of editing an existing document. That makes input settings more important than input text, because the settings are what define the shape of the result.

Generators are only as useful as the settings behind them. When the output seems off, check the count, range, delimiter, seed values, or pattern options before judging the result itself.

All processing happens in your browser, so your input stays on your device during the transformation.

Common Use Cases

• Add a row ID column as the first column of a dataset
• Prepend a source identifier when merging files from multiple systems
• Add a date stamp column to the front of periodic exports
• Insert a category or group label before existing data columns
• Add a batch number column for tracking data processing runs

How to Use

1. Paste your CSV data into the input area.
2. Enter the header name for the new column.
3. Optionally enter a default value to fill all rows.
4. Click Prepend and copy the result.

Features

• Adds columns at position 1, before all existing data
• Set custom header names
• Fill with default values or leave empty
• Prepend multiple columns at once
• Maintains all existing data unchanged

Examples

Below is a representative input and output so you can see the transformation clearly.

name,age,city
Ada,36,London
Lin,29,Berlin

id,name,age,city
1,Ada,36,London
2,Lin,29,Berlin

Edge Cases

• Very large inputs can still stress the browser, especially when the tool is working across many columns. Split huge jobs into smaller batches if the page becomes sluggish.
• Empty or whitespace-only input is technically valid but may produce unchanged output, which can look like a failure at first glance.
• If the output looks wrong, compare the exact input and option values first, because Prepend CSV Columns should be repeatable with the same settings.

Troubleshooting

• Unexpected output often means the input is being split or interpreted at the wrong unit. For Prepend CSV Columns, that unit is usually columns.
• If a previous run looked different, check for hidden whitespace, changed separators, or a setting that was toggled accidentally.
• If nothing changes, confirm that the input actually contains the pattern or structure this tool operates on.
• If the page feels slow, reduce the input size and test a smaller sample first.

Tips

When prepending a source identifier to distinguish merged files, use a unique value per file (like the filename or export date) so you can trace each row back to its origin.