# CSV rename columns

`csv-rename-columns` · version 1.0.0 · CSV & tables · free, no key needed

Rename CSV headers by an exact from/to mapping, preserving row cells and column order.

**Use when you need to: csv rename columns · rename csv columns · rename csv headers.**

## Supported

- csv rename columns
- rename csv columns
- rename csv headers

## Not supported

- fuzzy header matching
- case-insensitive rename
- infer new names
- drop columns
- reorder columns
- read files
- fetch urls

## Behavior

- mapping is a list of 1 to 256 { from, to } pairs; from and to are non-empty strings of at most 256 bytes.
- from values must be unique and each must equal a current header exactly; to values must be unique.
- A from equal to to is a no-op for that column. Column order and cell strings are unchanged.
- After rename, headers must remain unique; a to value must not collide with an unrenamed header.
- An empty document without a header is rejected; a header-only document is renamed and keeps zero data rows.
- The first output header name may not begin with U+FEFF because it is ambiguous with a CSV byte-order mark.

## Input

- `csv` (string, required): max length 256000
- `mapping` (array of object, required): min items 1; max items 256

## Output

- `csv` (string, required)

## Limits

- max input bytes: 256000
- max data rows: 5000
- max columns: 256
- max header name bytes: 256
- max mapping entries: 256
- max output bytes: 256000

## Example

Request input:

```json
{
  "csv": "id,name,note\n1,Ada,\"hello, world\"\n",
  "mapping": [
    {
      "from": "name",
      "to": "full_name"
    },
    {
      "from": "id",
      "to": "user_id"
    }
  ]
}
```

Response:

```json
{
  "result": {
    "csv": "user_id,full_name,note\n1,Ada,\"hello, world\"\n"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "csv-rename-columns",
  "version": "1.0.0",
  "input": {
    "csv": "id,name,note\n1,Ada,\"hello, world\"\n",
    "mapping": [
      {
        "from": "name",
        "to": "full_name"
      },
      {
        "from": "id",
        "to": "user_id"
      }
    ]
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/csv-rename-columns/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"csv":"id,name,note\n1,Ada,\"hello, world\"\n","mapping":[{"from":"name","to":"full_name"},{"from":"id","to":"user_id"}]}'
```

The machine-readable contract is at [/v1/tools/csv-rename-columns/versions/1.0.0](/v1/tools/csv-rename-columns/versions/1.0.0).

### CLI

```sh
node cli.mjs run csv-rename-columns 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [CSV concat](/tools/csv-concat): Concatenate CSV documents that share identical headers, preserving document and row order.
- [CSV dedupe](/tools/csv-dedupe): Remove duplicate CSV data rows while preserving the first occurrence.
- [CSV drop columns](/tools/csv-drop-columns): Drop named CSV columns and keep the remaining columns in original header order.
- [CSV fill defaults](/tools/csv-fill-defaults): Replace empty cells in named CSV columns with exact default strings.
- [CSV group count](/tools/csv-group-count): Count CSV rows by exact named-column tuples in first-seen order.
- [CSV merge columns](/tools/csv-merge-columns): Join named CSV columns with an exact separator into one column.