How is the target index counted?

0-based: index 0 inserts before the current first column, index 1 inserts after the current first column, and so on.

What happens if I give an index larger than the current column count?

It's clamped to the current width, so the column simply lands at the end rather than producing an error.

Do I need this instead of Column Prepender or Column Appender?

Only if you need a position other than the very start or very end. Prepender and Appender are simpler shortcuts for those two common cases.

What value does every data row get?

The exact fill value you type, repeated identically in every data row's new cell.

Does the header row also get a new cell?

Yes, at the same index, containing the header name you provide, so every row (including the header) stays the same width.

Are quoted fields with embedded commas handled correctly?

Yes, RFC 4180 quoting is respected on both parsing the input and re-serializing the output.

CSV Column Inserter - Insert a Column at Any Index

Overview

Introduction

Sometimes a new column doesn't belong at the start or the end, it needs to sit between two existing ones to match a template or a downstream schema. This tool inserts a column at exactly the index you specify.

It generalizes the "start" and "end" cases into one tool with a single extra number field: the target index.

What Is CSV Column Inserter?

A structural CSV tool that inserts one new column at any 0-based index in every row, using your chosen header name for row 0 and a repeated fill value for every data row.

Columns at or after the target index shift one position to the right to make room; columns before it are untouched.

How CSV Column Inserter Works

The input is parsed into a grid and padded to a uniform width, then the target index is clamped into the valid range `[0, width]`.

Each row is split at that index and a new cell is spliced in between the two halves, then the grid is re-serialized back into CSV text.

When To Use CSV Column Inserter

Use it when a target schema or import template expects a new field at a specific position, not just first or last.

It's also useful for reconstructing a column that was accidentally deleted, back at its original index.

Often used alongside CSV Column Prepender, CSV Column Appender and CSV Column Deleter.

Features

Advantages

Supports any target position, not just the start or end.
Out-of-range indexes are clamped rather than rejected, so you can't easily corrupt the output with a typo'd index.
Preserves RFC 4180 quoting on both read and write.

Limitations

Every data row gets the same fill value; there's no per-row value support in this tool.
Only comma-delimited CSV is supported.

Examples

Inserting a column at index 1

Input

id,amount
1,120
2,90

Output

id,name,amount
1,unknown,120
2,unknown,90

Inserting at index 1 places "name" (filled with "unknown") between the existing "id" and "amount" columns.

Best Practices & Notes

Best Practices

Double-check the target index against the header row's current column count before running, since off-by-one is the most common mistake here.
Use Column Prepender or Column Appender instead when you specifically mean index 0 or the last index, they're simpler shortcuts for those cases.
Follow up with CSV Column Replacer if different rows need different values in the new column.

Developer Notes

Implemented with `row.slice(0, at)` and `row.slice(at)` around the new cell, where `at = Math.min(index, width)` clamps any out-of-range input rather than throwing.

CSV Column Inserter Use Cases

Matching a new column's position to a fixed import template that expects fields in a specific order
Restoring a previously deleted column back to its original index
Building up a CSV's structure incrementally, one inserted column at a time

Common Mistakes

Off-by-one errors when counting the target index, remember it's 0-based and counts from the left.
Expecting per-row values from a single fill-value field; use CSV Column Replacer afterward for that.

Tips

If you're not sure of the exact index, insert at the end first with a placeholder, then use Column Swapper to move it into place.
Leave the fill value blank to insert an empty placeholder column.

CSV Column Inserter