CSV

CSV (Comma-Separated Values) is a plain-text format for tabular data where each line is a record and fields are separated by commas. It was informally used for decades before being loosely standardized as RFC 4180, which pins down the text/csv media type, header rows, and quoting rules. Its whole appeal is that it is the lowest common denominator of data exchange - anything from a spreadsheet to a database to a script can read and write it.

• Human- and machine-readable - A CSV file is legible in any text editor and parseable by nearly every language and tool.
• Tabular by nature - Rows and columns map cleanly onto spreadsheets, database tables, and dataframes.
• Loosely specified - RFC 4180 documents common practice but real-world CSV varies in delimiters, quoting, and encoding, so parsers must be forgiving.
• No types or nesting - Everything is text and flat, which keeps it simple but pushes typing and structure onto the consumer.

In API operations CSV is the workhorse of bulk and reporting endpoints - exports, data dumps, billing and analytics downloads, and import pipelines where a spreadsheet is the real client. Providers often expose it alongside JSON through content negotiation on the Accept header, offering the same dataset in a structured format for applications and a flat one for analysts. It is rarely the format for interactive APIs, but for moving whole datasets between systems it remains hard to beat.