Add a Column to a CSV

constant · row number · template · copy of a column · UUID · any position

Add the column a downstream system insists on. Stamp every row with a source name or an import batch, number the rows so you can restore this exact order later, generate an ID per row, or build a value from the columns you already have. Choose where it goes — first, last, or right after a specific column.

How to add a column

1. Paste the CSV or drop a file.
2. Name the column and pick what fills it.
3. Fill in value where the mode needs it: the constant itself, a template like {city}-{plan}, or the name of the column to copy.
4. Choose the position — the dropdown lists (first), every existing column, and (last). Then copy or download.

The fill modes

• Constant — the same value in every row. For tagging a file's origin (source=stripe), an environment, or an import date before you stack it with others in Merge files.
• Row number — a sequence with your own start and step. Add this before sorting and you can always get back to the original order.
• Template — {column} placeholders filled per row, e.g. {region}/{month} to build a grouping key.
• Copy of another column — duplicate a column so you can transform one copy and keep the original intact.
• UUID — a version-4 identifier per row, for seeding a table that needs surrogate keys. New values are generated on each run, so download once and keep that file.
• Nothing — an empty column, for when a strict importer requires the field to exist.

If the name is already taken

Duplicate header names break loaders and silently collapse into one column in most parsers, so a clashing name gets a numeric suffix instead: status becomes status_2, and the status line tells you it happened. To replace an existing column rather than add one, rename it away first with Header row, or drop it with Keep / rename / reorder.

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