CSV Output

Output

Write the incoming row stream to a .csv file. Pick the column delimiter, decide whether to write a header row, and choose between Unix (LF) or Windows (CRLF) line endings. Values containing the delimiter, quotes, or newlines are quoted automatically.

Local processing

This transform runs entirely in your browser. No data is sent to external servers.

How it works

CSV Output is a sink node — it consumes a row stream and produces a text/csv Blob the user can download. The headers are taken from the keys of the first row in the stream, in insertion order. Subsequent rows are written by reading those same keys; columns that appear later in the stream but not in the first row are silently dropped.

Each cell is converted to a string with the shared cellToString helper (null and undefined become empty strings, numbers and booleans use String()). A cell is quoted only if it contains the delimiter, a double quote, \n, or \r. Inside a quoted cell, embedded double quotes are doubled (" → ""). Otherwise the raw string is written.

Input: A row stream from any upstream transform. Output: A CSV Blob with MIME type text/csv.

Options

Option	Type	Default	Description
delimiter	string (1 char)	,	Single character used to separate columns. Common values: ,, ;, \t, |.
includeHeader	boolean	true	Write the column names as the first row.
lineEnding	"LF" | "CRLF"	"LF"	Line terminator. LF for Unix/Mac, CRLF for Windows.

Examples

Default comma-separated output with header

A standard CSV download — comma delimiter, header row, Unix line endings.

Before:

order_id	customer	amount
1001	Acme Corp	2400
1002	Beta Inc	750

Configuration: defaults — delimiter: ",", includeHeader: true, lineEnding: "LF".

After (raw file content):

order_id,customer,amount
1001,Acme Corp,2400
1002,Beta Inc,750

Quoting values that contain the delimiter

A row contains a comma in the customer name and embedded quotes in the note.

Before:

order_id	customer	note
2001	Acme, Corp	He said “ship today”
2002	Beta Inc	priority

Configuration: defaults.

After (raw file content):

order_id,customer,note
2001,"Acme, Corp","He said ""ship today"""
2002,Beta Inc,priority

The customer cell is wrapped in quotes because of the embedded comma. The note cell is wrapped because of the embedded quotes, and each " is escaped as "".

Tab-separated, no header, Windows line endings

A TSV export aimed at a Windows tool that expects CRLF and no header line.

Before:

date	label	amount
2025-04-01	rent	1200
2025-04-02	groceries	87

Configuration: delimiter: "\t", includeHeader: false, lineEnding: "CRLF".

After (raw file content, with → shown for tab and ␍␊ for CRLF):

2025-04-01→rent→1200␍␊2025-04-02→groceries→87

Tips and Edge Cases

• Header columns are locked to the first row. The output uses Object.keys(firstRow) as the column list and applies it to every subsequent row. If a later row introduces a new key, that key is omitted from the output. Normalise keys upstream (e.g. via Add Column with a default value) before serialisation. See apps/web/src/transforms/output-csv/logic.ts:96-114.
• null and undefined become empty strings. There is no null literal in CSV. Distinguishing missing data from empty strings is impossible after this step — record the distinction upstream if you need to recover it. See apps/web/src/transforms/output-csv/logic.ts:107-114 and apps/web/src/transforms/shared/cell-utils.ts.
• delimiter must be exactly one character. Multi-character separators are rejected at config-validation time. See apps/web/src/transforms/output-csv/logic.ts:18-22.

Related Transforms

• Excel Output — write .xlsx workbooks instead of plain CSV.
• JSON Output — write a JSON array or NDJSON when the consumer expects structured data.
• Reorder Columns — set the column order before serialisation, since CSV Output uses first-row key order.