# CSV fields that break a naive split

Commas inside fields, embedded newlines and escaped double quotes.

Category: DATA FORMATS
Canonical: https://fieldnotesarchive.org/wiki/csv-edge-cases

Splitting each line on commas only works for a restricted subset of CSV. In the commonly used quoted-field format, a field can contain commas and line breaks when enclosed in double quotes.

```text
name,note
Ada,"contains a comma, here"
Lin,"said ""hello"""
```

## Choose a dialect

Delimiter, character encoding, header presence and handling of empty fields should be explicit. Files described as CSV may use semicolons or tabs. Use a parser that supports the actual dialect.

## Do not infer missing values accidentally

An empty field, the literal string `null`, and the number zero are different values unless your application specifies otherwise. Preserve leading zeros in identifiers such as postal codes.

## Export for the recipient

Spreadsheet applications can interpret formula-like text as executable formulas. When exporting untrusted values for spreadsheet use, apply the receiving application's recommended protections and test the exported file.